\  ^ 


-^4 


/^ 


Digitized  by  the  Internet  Archive 

in  2011  with  funding  from 

Boston  Library  Consortium  IVIember  Libraries 


http://www.archive.org/details/radioforeverybodOOIesc 


RADIO  for  EVERYBODY 


T  ISTENING  to  the  foremost  citizens  of  the  nation; 
JLj  keeping  in  touch  with  the  affairs  of  the  world; 
enjoying  the  classical  and  popular  music  of  yesterday 
and  of  the  very  hour;  spanning  hundreds  and  even  thou- 
sands of  miles  withomt  physical  conductors  between  the 
talker  and  the  listener;  handling  current  by  the  kilowatt 
and  by  the  thousandth  of  a  watt;  starting  with  the 
simple  receiver  and  cuhninating  with  a  powerful  trans- 
mitter, even  one  capable  of  spanning  the  Atlantic,  as 
shown  in  this  painting — all  these  features  and  many 
others  make  radio  the  fascinating  subject  which  it  is  to 
layman  and  professional  alike.  •— ^ 


Radio 

for 

Everybody 


Being  a  popular  guide  to  practical  radio- 
phone reception  and  transmission  and  'o  the 
dot-and-dash  reception  and  transmission 
of  the  radio  telegraph,  for  the  layman 
who  wants  to  apply  radio  for  his  pleasure 
and  profit  without  going  in'o  the  special 
theories    and    the    intricacies    of    the    art. 


By  AUSTIN  C.  LESCARBOURA 

Managing  Editor,  Scientific  American 


SCIENTIFIC  AMERICAN  PUBLISHING  COMPANY 
MUNN  &  COMPANY 
.^    .  New   York 

1923 


BO^ON  COLLKGE  LTBRARf 


Copyright    19^2 

By 

Scientific    Americax    Publishing    Co. 


All   Rights    Reserved 


The    right    of    translation    into    all     languages, 
including  the   Scandinavian,   is   reserved. 


Printed  in  the  United   States  of  America 
by  the  Andrew  H.  Kellogg  Co.,  New  York 


PREFACE 

CLOTHES  and  books  —  good  clothes  and 
good  books,  to  be  sure  —  have  something 
very  much  in  common.  Both  must  be  made  to 
fit  a  very  definite  type  of  person  in  order  to 
prove  satisfactory.  So,  in  building  or  making 
a  suit  or  a  book  for  a  given  type  of  person,  it  is 
necessary  first  of  all  to  study  that  type,  take  all 
the  necessary  measurements,  learn  what  the  likes 
and  dislikes  happen  to  be,  and  in  every  way 
study  the  type  to  be  fitted.  Then,  with  all  these 
special  facts  in  hand,  there  remains  the  task  of 
building  or  making  a  suit  or  book  to  fit  the  type 
we  have  selected  or  the  type  that  has  selected  us. 
This  work  is  not  a  ready-made  product;  at 
least,  that  is  not  the  way  I  have  gone  about  put- 
ting it  together.  I  spent  some  time  studying  the 
reaction  of  the  general  public  to  radio,  follow- 
ing the  inauguration  of  the  first  radio-phone 
broadcasting  stations.    I  installed  a  radio-phone 


iv  PREFACE 

receiving  set  in  order  to  study  this  new  art  and 
its  practical  application  at  first  hand.  Indeed, 
the  manuscript  for  this  book  was  written  on  the 
very  table  on  which  I  have  my  radio  receiving 
set;  and  as  urgent  as  this  work  has  been  in  order 
to  have  it  appear  within  the  shortest  possible 
time  to  be  of  greatest  service  to  the  public,  I 
am  free  to  confess  that  I  have  been  unable  to 
resist  the  temptation  of  donning  the  head  'phones 
and  listening  in  on  the  radio-phone  concerts  at 
odd  moments.  So  the  work,  you  can  rest  as- 
sured, has  been  inspired  by  actual  contact  with 
the  new  art  and  with  the  persons  seeking  to 
gain  a  practical  knowledge  of  this  new  art.  The 
hundreds  and  thousands  of  inquiries  which  have 
found  their  way  to  the  editorial  rooms  of  the 
Scientific  American  alone,  not  to  speak  of 
conversations  with  persons  met  in  and  out  of 
business,  have  been  an  invaluable  guide  in  plan- 
ning this  work  to  fit  the  new  radio  layman. 

Radio-phone  broadcasting  has  changed  the 
aspects  of  radio.  A  year  or  more  ago,  radio 
appealed  to  the  boy  and  young  man  in  search 
of  some  intricate,  mysterious,  time-consuming 
hobby  in  which  to  invest  spare  moments  and 
inventive  ability.  These  radio  amateurs,  as  they 
are  called,  care  more  for  the  construction  and 


PREFACE  V 

wiring  and  theoretical  functioning  of  their  re- 
ceiving and  transmitting  equipment  than  they 
do  for  the  actual  signals  they  handle.  They 
look  upon  radio  as  an  engineering  study.  The 
radio-phone  music  and  dot-dash  messages  are, 
in  many  instances,  purely  incidental. 

But  our  present  radio-phone  concerts  have 
brought  a  new  element  into  radio.  What  with 
talks  by  prominent  men,  weather  forecasts,  crop 
and  market  reports  for  farmers,  bed-time  stories 
for  children,  shipping  news,  fashion  talks,  health 
chats,  musical  selections  and  other  features 
which  can  now  be  received  every  day  and  eve- 
ning right  in  the  home,  radio  has  become  a 
means  to  an  end.  That  end  is  the  entertainment 
and  educational  value  of  the  radio-phone  broad- 
casting service.  And  the  public  is  becoming 
more  and  more  interested  in  that  end,  and  with 
radio  only  so  far  as  it  is  necessary  in  order  to 
secure  the  radio-phone  service. 

However  that  may  be,  the  radio-phone  service 
is  a  radio  proposition.  It  calls  for  radio  ap- 
paratus and  some  knowledge  of  radio  com- 
munication as  a  whole,  just  as  the  owner  of  an 
automobile  should  have  a  general  knowledge  of 
the  mechanism  of  the  automobile,  even  though 
it  is  not  necessary  to  delve  deeply  into  the  minute 


vi  PREFACE 

construction  of  his  machine  and  into  the  expan- 
sive field  of  automotive  engineering.  What  is 
required  is  practical  and  helpful  information 
about  the  mechanism  with  Which  the  desired  re- 
sults are  obtained.     . 

This  work  has  been  written  with  that  very 
thought  in  mind.  It  has  been  built  or  made  for 
the  layman  who  wants  to  enjoy  radio-phone 
concerts  and  talks  and  bulletins  to  the  utmost, 
but  does  not  want  to  take  up  time  and  trouble 
studying  the  intricacies  of  radio  engineering.  It 
aims  to  give  the  essential  information  without 
the  theory  and  mathematics.  It  has  much  of 
interest  to  the  beginner  who  is  going  to  build 
or  buy  a  radio  set;  it  can  teach  not  a  few  things 
to  the  radio  devotee  who  possesses  a  radio  re- 
ceiving set  and  wants  to  learn  more  about  his 
set  and  better  sets;  it  may  possibly  have  some- 
thing of  interest  for  the  radio  amateur  who  has 
progressed  pretty  far  along  in  the  art,  although 
I  am  frank  to  say  that  for  the  dyed-in-the-wool 
radio  amateur  and  the  radio  engineer,  this  book 
is  no  doubt  too  elementary. 

I  take  this  opportunity  of  thanking  the  radio 
fraternity  as  a  whole  for  its  co-operation.  More 
particularly,  I  wish  to  thank  Mr.  Pierre  H. 
Boucheron  for  going  over  the  more  technical 


PREFACE  vii 

parts  of  this  book;  the  General  Radio  Company, 
the  Westinghouse  Electric  and  Manufacturing 
Company,  the  Radio  Corporation  of  America, 
the  Pacent  Electric  Company,  and  C.  Brandes, 
Inc.,  for  their  practical  co-operation  in  enabling 
me  to  obtain  much  of  the  following  data  at  first 
hand. 

In  reading  the  following  pages  of  this  little 
book  you  will,  I  hope,  obtain  as  much  pleasure 
from  its  practical  application  as  I  have  had  in 
gathering  the  material  together  and  writing  it 
for  you. 

The  Author. 
New  York, 
April  loth,  1922. 


CONTENTS 


CHAPTER  I. 
The  Elements  of  Radio  Reception  and  Trans- 
mission   1 

CHAPTER  H. 
Radio-Phone   Broadcasting — What   it   is  and 

What  it  Means 3^ 

CHAPTER  HL 
Dot-and-Dash    Broadcasting:    Erom     Market 

News  to  Time  Signals 73 

CHAPTER  IV. 
Receiving   Equipment   and   the   Interception 

OF  Radio  Waves 93 

CHAPTER  V. 
Operating  the  Radio  Receiving  Set  and  Mas- 
tering the  Telegraph  Code 143 

CHAPTER  VI. 
Making  .Big  Sounds  Out  of  Little  Ones,  or 

the  Gentle  Art  of  Amplifying 177 

CHAPTER  VII. 
Transmitting   the    Dot   and    Dashes    of   the 

Damped  Radio  Telegraph    205 


X  CONTENTS 

CHAPTER  VIII. 
The  Radio-Telephone  Transmitter  and  C.  W. 

Telegraph  Transmitter   229 

CHAPTER  IX. 
The  Unusual  Uses  of  Radio  on  Land  and  Sea 

AND  in  the  Air 247 

CHAPTER  X. 
Radio  in  Working  Clothes  or  the  Application 

OF  Radio  to  Everyday  Business 259 

CHAPTER  XI. 
How   TO    Construct    Simple   Radio   Receiving 

Sets  for  Radio-Phone  Programs 279 

CHAPTER  XII. 
The  Radio-Telephone  of  Today  and  Tomorrow     307 


Chapter  I. 

THE   ELEMENTS   OF   RADIO   RECEP- 
TION AND  TRANSMISSION 


AS  far  as  nine  persons  out  of  every  ten  are  concerned, 
the  main  interest  in  radio  is  to  receive  the  radio- 
phone music  and  talks.  Whether  the  receiving  set  is 
of  the  loose-coupled  type  or  whether  it  employs  the  Arm- 
strong regenerative  scheme  makes  little  or  no  difference. 
These  details  are  as  so  much  Latin  or  Greek  to  the 
average  person.  The  main  object,  after  all,  is  to  know 
just  what  kind  of  set  is  necessary,  how  simply  it  can  be 
installed,  and  what  it  will  cost.  Otherwise  stated,  the 
average  man  is  interested  first  and  last  in  the  performance 
and  not  in  the  thing  itself.  He  wants  to  receive  the 
radio-'phone  service  without  delving  into  the  intricacies 
of  radio — and  we  do  not  blame  him. 

It  should  be  that  way.  The  radio-phone  broadcasting 
service  has  given  radio  a  popular  mission  to  fulfill.  It 
has  brought  radio  out  of  the  laboratory  and  commercial 
world  and  introduced  it  into  the  home  circle,  there  to 
enlighten  and  to  entertain  as  nothing  else  ever  could. 
Formerly,  radio  was  known  and  appreciated  by  the  pub- 
lic at  large  in  a  very  general  and  vague  sort  of  way;  but 
it  was  only  on  rare  occasion  that  the  average  man  came 
into  intimate  contact  with  radio.  Certain  persons  who 
became  interested  in  radio  Avere  mostly  of  that  kind 
who  delve  deeply  into  intricate  things  and  master  numer- 
ous and  difficult  details.  They  have  an  engineering  or 
even  an  experimental  and  inventive  turn  of  mind.    Such 


2  RADIO  FOR  EVERYBODY 

persons  no  doubt  care  more  about  the  arrangement  and 
delicate  manipulation  of  the  components  of  their  receiv- 
ing sets  than  they  do  about  the  kind  of  messages  that  are 
picked  up.  Listening  to  a  radio-phone  service,  they  are 
thinking  all  the  while  in  terms  of  decrement  and  modula- 
tion and  continuous  wave  transmitters,  and  in  many  in- 
stances they  do  not  even  know  what  has  been  said  or 
played  at  the  end  of  the  performance !  Their's  is  a  real 
interest  in  radio  for  the  art's  sake,  but  they  are  decidedly 
in  the  minority. 

Today,  be  it  remembered,  the  radio-phone  service  be- 
longs to  everybody.  It  is  intended  for  the  public  at 
large.  And  by  the  same  token  that  branch  of  radio  ac- 
tivity for  which  it  stands  must  be  kept  devoid  of  techni- 
calities as  far  as  possible  if  it  is  to  expand  and  gain  still 
further  favor.  Devotees  of  the  radio-phone  look  upon 
the  broadcasting  service  just  as  they  would  the  phono- 
graph. When  they  purchase  a  phonograph  they  do  not 
have  to  learn  how  the  records  are  made,  what  makes  one 
record  better  than  another,  what  the  rate  of  vibration  is 
for  the  various  instruments  recorded  on  a  given  record, 
what  is  the  wave  form  of  each  instrument  as  impressed 
on  the  record,  and  so  on.  Their  interest  starts  and  ends 
with  the  desire  to  hear  music.  And,  notwithstanding  the 
intricacies  of  the  radiophone,  they  look  upon  the  radio- 
phone in  exactly  the  same  way. 

Radio  Without  A  Struggle — ^Can  it  be  Done? 

Let  us  have  no  illusions  on  the  subject.  Radio  is  a 
difficult  and  intricate  branch  of  engineering;  indeed,  it 
represents  the  highest  technique  in  applied  electricity. 
Hence  it  becomes  impossible  to  give  real,  helpful  informa- 
tion on  radio  reception  and  transmission,  yet  steer  clear 
of  such  formidable  terms  as  variometers,  condensers, 
regenerative  circuits,  logarithmic  decrement,  damped  and 
continuous  oscillations,  and  so  on.  However,  it  can  all 
be  explained  in  a  simple  and  elementary  way,  and  it  must 
be  done.     That,  precisely,  is  the  purpose  of  this  book. 


RADIO  FOR  EVERYBODY  3 

Starting  out  with  the  very  rudiments  of  the  art,  you,  the 
reader,  are  to  be  introduced  step  by  step  to  the  various 
phases  of  the  radio  art  until  you  have  mastered  the  essen- 
tial elements  of  the  subject.  Then,  should  you  desire  to 
delve  deeper  into  this  most  interesting  of  hobbies,  you  can 
readily  turn  to  the  more  advanced  works  which  are  now 
available  in  large  numbers. 

To  begin  with,  radio  communication,  whether  it  be  the 
radio-phone  or  the  radiogram,  is  based  on  a  cause  and  an 
effect,  separated  by  a  greater  or  less  distance.  The  cause 
is  the  transmitter,  which  sets  up  certain  disturbances  or 
waves  in  space  which  travel  in  all  directions  until  they 
reach  the  distant  point  and  create  the  desired  effect, 
which  is  the  result  obtained  with  the  receiving  set. 

In  the  instance  of  the  radio-phone  service,  the  cause 
is  the  radio-phone  broadcasting  station.  There  are  a 
number  of  such  stations  located  in  various  parts  of  the 
United  States;  indeed,  virtually  every  section  of  the 
country  is  now  served  with  music,  news  of  the  day, 
weather  forecasts,  crop  and  market  reports,  and  so  on. 
The  radio-phone  station  sets  up  disturbances  or  waves  in 
space  which  travel  in  all  directions.  These  disturbances 
or  waves  may  be  intercepted  at  any  point  within  the  range 
of  the  station,  and  when  so  intercepted  can  be  brought 
to  suitable  receiving  instruments  and  reconverted  into 
the  original  sounds  of  the  music  or  talk,  as  the  case  may 
be,  so  as  to  give  a  faithful  rendition  to  the  radio  audi- 
ence.   That  is  the  effect. 

Now,  just  how  the  disturbances  are  set  up  and  how 
they  travel  through  space  is  still  a  problematical  matter. 
Until  Einstein  came  along  and  upset  many  of  our  pet 
theories  with  which  we  had  explained  so  many  things 
during  several  generations  past,  it  was  usually  held  that  a 
radio  transmitter  set  up  vibrations  or  wave  motions  in 
ether.  Ether  is  the  name  given  to  a  hypothetical  sub- 
stance held  to  exist  everywhere,  even  in  a  vacuum.  But 
with  the  ether  explanation  rendered  more  or  less  obso- 
lete by  the  said  Einstein,  as  well  as  by  certain  astronomi- 


4  RADIO  FOR  EVERYBODY 

cal  experiments  which  have  produced  interesting  and  tell- 
ing results  by  way  of  confirming  Einstein's  theories,  our 
pet  radio  explanation  has  been  rather  shattered. 

Still,  for  all  practical  purposes  we  can  state  that  cer- 
tain kinds  of  waves  of  an  electromagnetic  character  are 
produced  by  a  radio  transmitter,  and  that  these  waves 
travel  through  space  at  186,000  miles  per  second.  These 
waves,  too,  have  much  the  same  characteristics  as  the 
waves  which  we  call  light,  except  as  regards  their  wave 
length  and  as  regards  their  frequency  of  vibration. 
Whereas  the  waves  of  visible  light  have  a  length  to  be 
measured  in  niillionths  of  a  millimeter,  and  a  frequency 
of  vibration  of  billions  per  second,  the  waves  used  in 
radio  work  are  seldom  less  than  100  metres  in  length,  and 
may  be  as  long  as  20,000  meters  or  more  in  the  case  of 
long-distance,  high-power  transmitters  such  as  span  the 
Atlantic.  At  the  same  time  the  frequency  of  radio  waves 
is  to  be  measured  in  millions  down  to  thousands  per  sec- 
ond. These  radio  waves  pass  through  space  and  pretty 
much  through  everything  that  stands  in  their  way.  They 
pass  through  stone  walls,  frame  buildings,  mountains, 
forests,  and  so  on.  Certain  things,  particularly  masses 
of  metal  such  as  a  huge  steel  structure,  absorb  a  consid- 
erable volume  of  the  radio  waves,  especially  those  of  short 
wave  length,  but  there  is  always  a  sufficient  volume  left 
to  affect  all  receiving  sets  within  range. 

The  radio  waves  are  everywhere,  yet  cannot  be  seen 
or  felt.  Without  a  receiving  set  it  is  impossible  to  tell 
if  the  air  is  permeated  with  radio  traffic  or  whether  it 
is  absolutely  barren.  So  far  as  is  known,  even  the 
strongest  radio  waves  have  no  direct  effect  on  any  of  the 
five  senses,  which  are  the  sole  avenues  whereby  we  ap- 
preciate anything  that  is  external  to  ourselves.  Directly, 
we  cannot  feel,  hear,  smell,  taste  or  see  the  radio  waves. 
While  it  is  true  that  the  eye  is  a  detector  of  electro- 
magnetic waves  such  as  light  consists  of,  still,  the  unaided 
eye  can  only  detect  the  very  short  waves  of  visible  light 
which,  as  already  mentioned,  are  minutely  short  and  are 


RADIO  FOR  EVERYBODY  5 

all  contained  within  the  narrow  limits  of  a  single  octave ; 
and  while  by  means  of  certain  luminous  screens  known 
as  fluorescent  screens  the  range  of  visibility  can  to  some 
extent  be  increased,  no  such  method  will  render  visible 
even  the  shortest  of  the  waves  used  in  radio. 

Radio  and  the   Pond  of  Still  Water 

Other  methods  have  had  to  be  developed  to  detect 
radio  waves.  These  methods  intercept  the  radio  waves 
and  convert  them  into  some  form  of  energy  which  will 
come  within  the  scope  of  our  senses.  The  receiving  set 
presents  the  usual  means  of  converting  radio  waves  into 
sound  waves  which  affect  the  human  ear. 

Now  let  us  consider  a  pond  of  still  water  as  space, 
in  order  to  follow  the  formation  and  propagation  of  radio 
waves.  When  a  pebble  is  thrown  into  the  smooth  water 
it  starts  a  series  of  concentric  ripples  or  waves,  which 
spread  out  indefinitely  with  a  speed  of  a  few  hundreths 
of  a  yard  per  second,  Similarly,  the  electro-magnetic 
disturbance  set  up  by  a  radio  transmitter  spreads  out  in 
all  directions  in  ever  increasing  circles,  at  the  astounding 
speed  of  186,000  miles  per  second — virtually  instantane- 
ous, in  the  practical  sense.  As  the  waves  spread  out 
over  the  pool,  little  bits  of  straw  or  grass  may  be  seen 
to  move  as  the  waves  reach  them.  These  bits  of  straw 
or  grass  may  be  compared  with  the  radio  receiving  sta- 
tions which  are  also  afTected  as  the  radio  waves  reach 
them. 

It  will  be  noted  that  the  waves  in  the  pond  grow 
weaker  as  they  extend  farther  and  farther  away  from  the 
point  where  the  pebble  was  thrown  into  the  water.  The 
same  thing  occurs  in  radio ;  as  the  waves  spread  farther 
and  farther  away  from  the  transmitter,  they  become 
weaker  until  they  no  longer  have  sufficient  power  to  actu- 
ate a  receiving  set.  Here,  then,  is  an  important  pomt 
to  bear  in  mind.  The  waves  become  weaker  with  dis- 
tance. Thus  at  a  short  distance  from  a  powerful  trans- 
mitter, a  relatively  crude  receiving  set  can  be  employed  to 


6  RADIO  FOR  EVERYBODY 

detect  the  powerful  waves.  At  a  greater  distance,  the 
same  relatively  crude  receiving  set  no  longer  responds  to 
the  attenuated  waves.  At  a  still  greater  distance  the 
waves  are  so  weak  that  they  do  not  produce  proper  re- 
sponse in  better  receiving  sets,  and  it  becomes  necessary 
to  resort  to  some  form  of  amplifying  device  for  the  pur- 
pose of  building  up  the  strength  of  the  waves  in  order  to 
obtain  the  proper  degree  of  audibility. 

All  of  which  indicates  that  the  question  of  distance  in 
radio  communication  is  governed  by  several  factors.  Be- 
ginners in  radio  will  insist  on  being  informed  how  far 
this  receiver  will  work  and  how  far  that  trarjsmitter  can 
send,  and  they  are  always  disappointed  when  told  that 
questions  such  as  these  are  not  answerable.  First  of  all, 
a  receiving  set  cannot  determine  the  distance  over  which 
it  will  receive.  From  a  powerful  transmitter  it  may  re- 
ceive over  a  distance  of  1,000  miles,  but  from  a  small 
amateur  transmitter  it  may  receive  over  a  distance  of  only 
25  miles.  It  is  the  transmitter,  then,  that  determines  the 
receiving  range.  On  the  other  hand,  the  transmitter  may 
actuate  a  high-grade  receiving  set  at  a  distance  of  1,000 
miles,  but  a  cheap  set  will  not  be  actuated  at  a  greater  dis- 
tance than  100  miles.  Again,  atmospheric  conditions  have 
much  to  do  with  the  range.  Under  ideal  conditions  the  dis- 
tances covered  may  be  three  times  the  usual  spans.  Hence 
in  all  questions  of  receiving  or  transmitting  ranges,  it  is 
necessary  to  take  the  receiving  set,  the  transmitter,  and 
the  atmospheric  conditions  into  consideration  in  order  to 
obtain  a  satisfactory  answer.  There  is  no  definite  range 
for  any  given  instrument ;  specific  conditions  at  any  given 
moment  decide  the  range.  Otherwise,  all  statements  of 
ranges  must  be  approximations  of  a  very  crude  sort. 

The  Important  Question  of  Wave  Length 

Returning  to  the  pool  of  water,  it  will  be  noted  that 
the  waves  in  spreading  out  from  the  transmitter  maintain 
a  certain  distance  between  themselves.  If  the  distance 
from  the  crest  of  one  wave  to  the  crest  of  another  is 


RADIO  FOR  EVERYBODY  7 

measured,  we  obtain  the  wave  length,  as  in  a — b  in  the 
accompanying  sketch.  In  the  case  of  the  waves  in  water, 
the  w^ave  length  is  determined  by  the  size  of  the  stone, 
the  wave  length  being  greater  when  a  larger  stone  is 
dropped  into  the  water.  In  radio,  however,  the  wave 
length  has  nothing  to  do  with  the  size  of  the  transmitter, 
although  it  is  true  that  short  wave  lengths  are  employed 
for  the  smaller  amateur  transmitters,  and  longer  wave 
lengths  for  the  commercial  stations,  especially  the  huge 
transatlantic  stations.  While  the  waves  are  larger  and 
therefore  more  powerful  when  a  large  transmitter  is  em- 
ployed, the  wave  length  is  determined  by  other  factors 
as  will  be  explained  further  on. 


What  happens   when   a  pebble  and  a  large   stone  are   dropped 

in   still  water.     Note  how^  the  pebble  causes   small  waves,   and 

the    large    stone    large    waves.      Measured    from   crest    to    crest. 

such    as    a — b,    we    obtain    the    wave    length    of    the    waves. 


The  wave  length  determines  the  tuning  of  the  trans- 
mitter and  receiver  alike.  Tuning  is  such  a  confusing 
term  to  the  layman,  yet  nothing  could  be  simpler  to 
understand.  Tuning  is  nothing  more  than  the  adjusting 
of  a  receiver  or  transmitter  to  a  given  wave  length,  so 
that  it  will  receive  that  wave  length,  in  the  case  of  the 
receiver,  and  transmit  that  wave  length,  in  the  case  of 
the    transmitter.      Thus    a    transmitter    is    adiusted    to 


8  RADIO  FOR  EVERYBODY 

200-meter  wave  length.  The  waves  emitted  by  that  trans- 
mitter are  of  200  meters  wave  length.  As  they  travel 
through  space  in  all  directions,  they  are  intercepted  by 
receiving  sets.  However,  only  those  receiving  sets  that 
are  tuned  to  200-meter  wave  length  receive  the  signals 
from  the  transmitter  in  question.  Other  receiving  sets. 
tuned  to  a  shorter  or  longer  wave  length,  do  not  respond. 
On  the  other  hand,  if  another  transmitter  is  sending  at 
the  same  time  on  a  600-meter  wave  length,  then  the 
first  batch  of  receiving  sets,  adjusted  to  200-meter  wave 
length,  will  not  respond  to  this  second  transmitter  but 
will  keep  right  on  receiving  from  the  200-meter  wave 
length  transmitter.  Other  receivers,  adjusted  to  the  600- 
meter  wave  length,  will  receive  from  the  second  trans- 
mitter, and  so  it  goes. 

It  is  tuning  that  has  made  practical  radio  communi- 
cation possible.  Were  it  not  for  tuned  waves,  it  would 
be  impossible  for  more  than  one  transmitter  to  operate 
in  a  given  area,  for  the  simple  reason  that  confusion 
would  result  if  other  transmitters  operated  at  the  same 
time.  Now,  with  tuned  waves,  several  transmitters  can 
operate  at  the  same  time,  and  the  receiving  sets  can  be 
adjusted  so  that  only  the  desired  transmitters  are  inter- 
cepted and  heard.  Thus  the  radio  broadcasting  stations 
generally  operate  on  360-meter  wave  length.  Amateur 
transmitters  are  by  law  limited  to  200-meter  wave  length 
or  less.  Commercial  stations  operate  on  higher  wave 
lengths.  By  dividing  the  wave  'length  field  into  various 
classes,  a  'minimum  of  interference  results  between  trans- 
mitters. One  can  spend  an  entire  evening  listening  to  a 
radio-phone  broadcasting  station  with  hardly  any  inter- 
ference from  radio  /telegraph  stations,  thanks  to  the  360 
meter  wave  length  reserved  for  radio-phone  service. 

Another  question  which  rather  confuses  the  beginner 
in  radio  is  whether  there  is  a  limit  to  the  number  of 
receiving  stations  that  can  listen  in  to  a  transmitter.  As 
a  matter  of  fact,  there  is  no  limit — at  least  in  practice. 
Any  number  of  receiving  stations  can  be  operating  at  the 


RADIO  FOR  EVERYBODY  9 

same  time,  picking  up  the  signals  or  music  from  one 
transmitter.  Furthermore,  the  transmitting  operator  can- 
not tell  how  many  receiving  sets  are  listening  to  what  he 
is  sending.  He  simply  sends,  and  there  is  no  telling  how 
far  his  signals  are  going  or  how  many  persons  are  listen- 
ing in. 

Damped  and  Undamped  Waves — Which? 

The  waves  dealt  with  so  far  in  the  pool  of  water  are 
highly   damped.     Which   means,   in   plain  language,   that 


The    difference    between    damped    or    discontinuous    waves,    and 

undamped   or  continuous  Avaves  in  water.     Dropping   a  pebble 

into  water  causes  damped  waves,  while  using  a  paddle  steadily 

produces   continuous   waves. 

they  die  down  quickly.  The  pebble  is  dropped  in  the 
pool  of  water,  and  the  waves  created  reach  but  a  short 
distance  away  before  they  have  virtually  disappeared. 
In  order  to  keep  up  a  disturbance  in  the  water,  it  is 
necessary  to  drop  one  pebble  after  another,  so  as  to 
create  a  steady  supply  of  waves,  represented  by  groups  or 
trains.  Each  group  or  train  soon  dies  down,  and  is  fol- 
lowed by  the  next  one,  and  so  on. 

In  radio,  we  have  the  same  condition  when  the  usual 
spark  transmitter  is  employed.  The  group  or  train  of 
waves  starts  out  strong  but  soon  dies  down,  and  a  second 
train  of  waves  must  be  started,  only  to  die  in  the  same 
manner.  Such  damped  waves  may  be  likened  to  the  ac- 
tion of  a  pendulum.  When  the  pendulum  is  given  a 
push,  it  swings  from  side  to  side,  but  each  swing  is  a 
trifle  shorter  than  the  preceding  one,  until  the  pendulum 
comes  to   a   dead   stop.     Its   action   is  damped,   in  other 


10  RADIO  FOR  EVERYBODY 

words,  and  corresponds  precisely  to  the  action  of  damped 
radio  transmitters. 

Of  late  years  the  undamped  transmitter  has  gained 
much  favor  in  radio.  Unlike  the  damped  transmitter, 
the  undamped  type  produces  a  steady  flow  of  waves. 
There  are  no  groups  or  trains.  It  is  just  as  though  a 
paddle  were  used  in  the  pool  of  water,  said  paddle  being 
worked  back  and  forth  so  as  to  produce  a  steady  series 
of  waves,  all  of  the  same  size  and  strength,  with  a 
uniform  wave  length  maintained  throughout.  Or  again, 
as  though  the  pendulum  were  given  a  fresh  push  at  each 
swing,  so  as  to  restore  the  initial  energy,  and  in  that 
manner  it  would  not  die  down  just  so  long  as  the  energy 
was  supplied. 

Undamped  wave  transmitters  are  employed  in  many 
commercial  and  amateur  transmitters.  They  are  also 
known  as  continuous  wave  transmitters  or  CW  trans- 
mitters for  short.  Radio  telephony  is  always  carried  on 
by  means  of  a  continuous  wave  or  undamped  wave  trans- 
mitter. In  the  case  of  the  undamped  wave  telegraph 
transmitter,  the  steady  flow  of  waves  is  altered  into  short 
and  long  trains  to  represent  the  dots  and  dashes  of  the 
telegraph  code.  In  the  case  of  the  radio  telephone,  how- 
ever, the  steady  supply  of  waves  is  modulated  or  varied 
by  means  of  a  telephone  microphone,  such  as  the  trans- 
mitter of  the  usual  telephone  instrument,  in  order  to 
impress  the  characteristics  of  music  or  speech  on  the  con- 
tinuous waves. 

Electricity  may  be  made  to  vibrate  or  oscillate  and  it  is 
this  vibration  or  oscillation  that  creates  radio  waves.  Cur- 
rent from  a  storage  battery  or  dry  battery  flows  steadily 
and  only  in  one  direction.  Current  flows  out  of  one  ter- 
minal of  the  battery,  through  the  circuit,  and  back  to  the 
other  terminal  of  the  battery.  That  is  direct  current. 
However,  there  is  another  form  of  current  known  as  al- 
ternating current,  which  is  generated  by  machines  known 
as  alternators,  and  by  other  methods.  Alternating  current 
does  not  flow   steadily,   nor   does   it   maintain  the   same 


RADIO  FOR  EVERYBODY  11 

direction  of  flow.  At  one  instant  the  alternating  current 
is  flowing  through  the  circuit  in  one  direction,  and  the 
next  instant  it  is  flowing  in  the  opposite  direction,  only 
to  change  back  to  the  first  direction  the  next  insiant,  and 
so  on.  Each  complete  change  of  direction  is  known  as  a 
cycle.  Commercial  alternating  current,  which  is  generally 
used  for  lighting  and  power  purposes  in  most  sections 
of  the  country  today,  is  known  as  60-cycle  current;  that 
is  to  say,  it  has  gone  through  60  cycles  of  change  in  one 
second,  each  cycle  consisting  of  a  rise  in  positive  voltage 
from  0  to  the  maximum  voltage  and  a  fall  to  zero,  and 
then  a  reversal  with  a  negative  rise  in  voltage  from  0 
to  -the  maximum  voltage,  and  back  to  0  again,  and  a 
repetition  of  the  performance  for  the  next  cycle. 

Vibrating  or  oscillating  currents  of  this  kind  are  neces- 
sary to  produce  radio  waves.  However,  the  rate  of  vi- 
bration or  oscillation,  or  the  frequency,  to  use  the  radio 
term,  must  be  of  a  much  higher  order  than  the  60-cycle 
frequency  of  lighting  and  power  circuits.  Thus  the  200- 
meter  wave  length  of  the  usual  amateur  transmitter  repre- 
sents 1,500,000  cycles  per  second,  while  the  10,000-meter 
wave  length  of  a  highpower  station-  represents  30,000 
cycles  per  second*.  It  will  be  noted  that  the  frequency  or 
number  of  cycles  ^er  second  determines  the  wave  length. 
The  frequency,  on  the  other  hand,  in  both  the  receiver 
and  the  transmitter  is  determined  by  two  factors,  known 
as  inductance  and  capacity. 

Inductance  is  the  length  of  conductor  in  a  circuit,  so 
far  as  the  layman  is  concerned,  and  we  must  keep  to 
simple  explanations  in  this  work  if  we  are  to  live  up 
to  its  title.  Thus  if  we  have  100  feet  of  wire  in  a  cir- 
cuit, we  have  four  times  as  much  inductance  as  in  the 
same  kind  of  wire  25  feet  long.  Inductance,  for  the  sake 
of  convenience,  is  generally  arranged  in  the  form  of 
a  spiral  or  a  helix  for  the  transmitter,  using  heavy 
conductor  since  the  current  being  handled  is  rather  a 
powerful  one;  for  receiving  purposes,  on  the  other  hand, 
the  inductance  is   in  the   form  of  insulated  wire  wound 


12  RADIO  FOR  EVERYBODY 

on  tubes  or  wound  in  compact  spools  or  coils  for  ready 
handling. 

The  capacity  is  the  ability  of  the  circuit  to  store  elec- 
tricity. Capacity  is  generally  represented  by  a  condenser, 
which  is  a  reservoir  or  storage  for  electricity.  In  fact, 
the  condenser  is  a  real  reservoir  or  storage  for  electricity. 
The  storage  battery  is  something  entirely  different,  al- 
though it  does  serve  to  store  electricity.  It  accomplishes 
this  end  by  causing  certain  chemical  changes,  and  these 
chemical  changes  in  turn  generate  electric  current  which 
may  be  drawn  from  the  battery  until  it  is  restored  to  its 
original  chemical  condition,  or  completely  discharged. 
Thus  the  current  proper  is  not  stored :  it  only  serves  to 
create  certain  chemical  conditions.  For  most  practical 
purposes,  however,  the  storage  battery  is  the  only  means 
available   for  storing  ordinary  current. 

The  condenser  is  always  made  up  of  sheets  of  brass, 
aluminum,  copper  or  tinfoil,  separated  by  some  non-con- 
ductor of  electricity,  referred  to  as  the  dielectric.  A  cer- 
tain number  of  metallic  sheets  are  connected  to  one  side  of 
a  circuit,  while  the  same  number  of  metallic  sheets  are  con- 
nected to  the  other  side.  The  non-conducting  material  or 
dielectric  separates  two  sets  of  sheets..  Between  the  sheets 
of  metal  there  is  created  a  static  pressure.  This 
pressure  accumulates  or  becomes  greater  until  the  con- 
denser, no  longer  capable  of  retaining  the  pressure,  dis- 
charges the  accumulated  electricity  back  through  the  cir- 
cuit of  which  it  forms  part.  The  discharged  current 
flows  through  the  circuit  from  one  set  of  plates  to  the 
other,  and  recharges  the  condenser  with  the  opposite 
polarity.  No  sooner  is  the  recharging  accomplished, 
when  the  condenser  discharges  again,  this  time  in  the 
opposite  or  original  direction,  of  course,  and  so  it  goes, 
until  the  charge,  getting  weaker  with  each  discharge,  is 
entirely  spent.  All  this  can  take  place  in  a  fraction  of  a 
second.  Thus  the  discharge  from  a  condenser  takes  the 
form  of  a  vibrating  current  or  oscillating  current,  which 
is  the  basis  of  radio  waves. 


RADIO  FOR  EVERYBODY  13 

The  Antenna  or  Aerial 

Let  us  return  for  a  moment  to  our  pond  of  still  water. 
Instead  of  a  pebble,  let  us  use  a  hinged  paddle  which 
can  be  moved  back  and  forth  to  create  waves.  This 
paddle  then  becomes  the  agency  for  transferring  power  to 
the  pool,  which  is  the  medium  for  distributing  the  waves. 
In  radio  the  energy  for  creating  the  waves  is  generated 
by  the  transmitter,  and  a  system  of  elevated  and  insu- 
lated wires,  known  as  the  aerial,  serves  to  impart  the 
energy  or  waves  into  space.  An  aerial  or,  as  it  is  more 
popularly  called  in  the  case  of  the  receiving  end  of  radio, 
an  antenna,  is  employed  at  the  receiving  end  to  inter- 
cept the  waves  and  to  bring  the  energy  down  to  the 
receiving  set.  The  receiving  antenna  may  be  likened  to  a 
hinged  paddle  at  some  remote  point  from  the  first  paddle 
creating  weaves  in  water.  The  receiving  paddle  is  pro- 
vided with  a  bell.  As  the  waves  travel  over  the  pond 
and  finally  reach  the  receiving  paddle,  they  cause  the 
paddle  to  sway  and  this  action,  in  turn,  rings  the  bell. 
This  action  is  precisely  that  of  the  receiving  antenna  and 
the  actuating  of  the  receiving  set. 

Aside  from  the  aerial  or  the  antenna,  a  ground  con- 
nection is  required  in  radio  communication.  The  ground 
side  means  a  good  connection  with  any  object  that  runs 
into  the  ground,  such  as  a  water  pipe  or  a  gas  pipe,  or  even 
some  object  which  is  eventually  connected  with  the  ground, 
such  as  steam-heating  pipe.  In  the  country,  where  such 
pipes  are  not  available,  a  good  ground  may  be  secured  by 
fastening  a  wire  to  a  bucket  which  is  dropped  into  a  well  or 
other  body  of  water.  Again,  an  iron  rod  may  be  driven 
down  into  moist  soil,  or  a  large  sheet  of  copper  or  gal- 
vanized iron  may  be  buried  in  moist  soil.  However,  the 
securing  of  a  good  ground,  as  well  as  the  construction 
of  the  aerial  or  antenna,  is  reserved  for  other  chapters. 

In  reality,  the  aerial  and  the  ground  form  a  con- 
denser. The  aerial  and  the  ground  are  the  plates  of  the 
condenser,  while  the  space  between  is  the  non-conductor  or 
insulator  or  dielectric,  whichever  you  wish  to  call  it.     To 


14  RADIO  FOR  EVERYBODY 

create  radio  waves  it  is  necessary  to  have  two  surfaces 
separated  by  a  distance  of  from  ten  to  several  hundred 
feet  and  to  create  between  them  an  electric  pressure  which 
changes  its  direction  first  toward  one  surface,  then  toward 
the  other.  In  other  words,  we  must  have  a  condenser 
effect.  The  current  must  change  direction  several  thou- 
sand times  per  second.  The  aerial  and  the  ground  af- 
ford just  such  an  arrangement,  and  between  these  we 
create  an  electric  pressure  of  from  one  to  20,000  volts 
by  means  of  a  suitable  transmitting  equipment,  which 
starts  waves  radiating  out  in  all  directions.  These  pres- 
sure waves  are,  however,  only  part  of  a  radio  wave. 
From  any  wire  in  which  current  is  flowing  electro-mag- 
netic waves  are  radiated ;  therefore,  radio  waves  are  made 
up  of  both  electro-magnetic  and  pressure  electro-static 
waves.  The  creation  of  these  waves  may  be  compared  to 
the  action  of  hurling  the  pebble  into  the  pond  of  still 
water,  as  already  explained.  The  amperes  (the  measure 
of  current  flow)  put  into  the  aerial  corresponds  to  the 
size  of  the  pebble,  while  the  volts  (the  pressure  or  poten- 
tial of  an  electric  current)  are  equivalent  to  the  force 
with  which  the  pebble  is  hurled.  The  larger  the  pebble 
and  the  greater  the  force  behind  it,  the  bigger  the  splash 
and  the  consequent  waves.  The  more  amperes  of  cur- 
rent flowing  in  the  aerial  circuit  and  the  greater  the 
pressure  in  volts  between  the  aerial  and  the  ground,  the 
stronger  the  waves  radiated  and  the  farther  they  will 
travel. 

Elements  of  Radio  Communication 

So  far,  so  good.  In  order  to  make  use  of  radio  waves 
for  the  practical  purposes  of  sending  messages  and  then 
receiving  them  at  a  distant  point,  it  is  necessary: 

(a)  To  produce  regular  electrical  disturbances  in  a 
circuit  which  starts  the  waves.  These  disturbances  are 
electrical  currents  which  reverse  rapidly  in  direction,  or 
vibrate,  so  to  speak.  In  radio  parlance  this  characteris- 
tic is  known  as  oscillating,  and  we  speak  of  transmitting 


RADIO  FOR  EVERYBODY  15 

circuits  as  oscillating-  circuits,  and  of  transmitters  as  os- 
cillators. The  rapidity  of  the  reversal  determines  the 
wave  length,  as  we  have  already  learned. 
■(b)  To  get  the  waves  into  surrounding  space,  through 
which  they  travel  with  great  speed.  This  is  done  by 
means  of  the  transmitting  aerial,  which  will  be  described 
further  on. 

(r)  By  means  of  these  waves,  to  set  up  electric  cur- 
rents in  a  receiving  circuit  at  a  distant  station.  The 
device  which  these  waves  strikes  as  they  come  in,  and 
which  turns  them  over  to  the  receiving  circuit,  is  called 
the  receiving  antenna  or  aerial. 

(d)  To  change  these  currents  so  that  they  may  be 
detected  by  suitable  apparatus.  The  operator  usually  re- 
ceives the  messages  through  sounds  in  a  telephone  re- 
ceiver. 

There  are  various  ways  in  which  radio  waves  may  be 
set  up.  The  simplest  consists  of  a  spark  coil,  such  as 
the  type  employed  in  automobile  ignition  systems ;  a  con- 
denser represented  by  the  aerial  and  the  ground,  and  a 
soark  gap  arranged  as  shown  in  the  accompanying  diagram. 
The  spark  coil  has  two  windings,  namely,  a  primary  and  a 
secondary.  To  the  primary  coil,  which  consists  of  a  rela- 
tively small  number  of  turns  of  wire  wound  about  the 
iron  core  of  the  coil,  are  connected  the  battery  supply- 
ing the  initial  current  and  the  vibrator  or  interrupter, 
which  breaks  up  the  current  flow  from  the  battery.  The 
secondary  consists  of  a  large  number  of  turns  of  wire 
wound  over  the  primary  winding.  In  the  nature  of  elec- 
trical things,  when  current  is  passed  through  the  primary, 
a  high  voltage  current  is  produced  in  the  secondary  wind- 
ing. The  primary  current  may  be  only  six  volts,  but 
the  secondary  winding  produces  perhaps  5  to  10,000  volts. 
This  stepping  up  of  the  voltage  is  a  necessary  part  of 
radio  transmitting.  Transformers  are  larger  devices  in- 
tended for  stepping  up  the  voltage  of  heavy  currents. 

At  any  rate,  high  volta?e  current  is  produced  in  the 
secondary  winding.    The  interrupter  causes  the  secondary 


16 


RADIO  FOR  EVERYBODY 


to  flow  first  in  one  direction,  and  then  in  the  other,  as 
the  primary  current  is  interrupted.  The  secondary  cur- 
rent, flowing-  for  a  moment  in  one  direction,  charges  the 
condenser,  consisting  of  aerial  and  ground.  However, 
the  capacity  of  the  condenser  is  limited,  and  when  it  is 
charged  to  overflowing,  it  releases  its  energy  which  jumps 
the  spark  gap  in  the  form  of  a  fat  spark,  only  to  pile 
up  on  the  other  side  of  the  condenser.  Again  the  con- 
denser is  filled  to  overflowing,  and  it  discharges  once 
more,  this  time  causing  the  current  to  flow  in  a  direction 


Ground 


The    essentials    of    transmitting    radio    signals,    comprising    a 

spark  coil,  aerial,  ground,  spark  gap,  key,  and  battery,  as  well 

as   an   inductance  coil  for  tuning   purposes. 

opposite  to  that  of  the  first  time,  and  again  the  condenser 
is  charged.  Thus  the  discharges  take  place  back  and 
forth,  but  far  faster  than  it  takes  to  explain  their  action 
here.  Indeed,  the  discharges  travel  back  and  forth  with 
the  speed  of  light,  but  gradually  diminish  in  strength  until 


RADIO  FOR  EVERYBODY  17 

the  charge  is  exhausted.  Every  time  the  vibrator  in  the 
primary  circuit  makes  or  breaks  the  current  in  the  prim- 
ary, one  of  these  trains  of  alternating-  current  or  oscilla- 
tory current  is  started.  Since  they  die  down  rapidly, 
they  are  known  as  damped  oscillations.  Each  one  of 
these  trains  produces  a  single  tick  in  the  distant  receiving 
station  telephone,  and  it  is  the  rapidity  with  which  these 
trains  follow  one  another  that  characterizes  the  "spark" 
or  sound  of  a  transmitter.  If  we  increase  the  capacity 
or  the  inductance  in  the  transmitting  circuit,  we  increase 
the  wave  length,  just  as  the  increasing  of  the  length  or 
the  weight  of  the  pendulum  affects  its  rate  of  swing. 

In  actual  practice  the  transmitter  is  connected  to  the 
aerial  and  ground.  The  oscillations  charge  the  aerial 
and  the  ground,  which  act  just  as  a  huge  condenser,  as 
already  explained.  The  longer  the  aerial,  the  longer  the 
wave  length  of  the  aerial  by  itself.  This  is  known  as  its 
natural  wave  length,  as  distinguished  from  what  its  wave 
length  may  be  raised  to  or  lower  to  by  external  capacity 
and  inductance.  The  waves  travel  out  from  the  aerial 
through  space,  and  through  the  ground  to  the  various  re- 
ceiving stations. 

These  waves  can  be  intercepted  at  any  point  within 
range  of  the  transmitting  station.  Obviously,  the  waves 
become  weaker  as  they  travel  out  from  the  transmitter. 
A  short  distance  away,  the  waves  may  be  intercepted  by 
an  inexpensive  and  relatively  crude  receiving  set,  but  at 
a  greater  distance,  when  the  waves  are  considerably 
weaker,  a  more  elaborate  and  more  sensitive  receiving  set 
must  be  employed. 

For  receiving  the  waves,  an  antenna  and  a  ground  con- 
nection are  necessary.  The  first  step  is  to  tune  the  an- 
tenna-ground circuit  so  as  to  bring  it  into  harmony  or 
resonance  with  the  desired  waves.  When  this  is  done, 
the  waves  flow  down  from  the  antenna  to  the  ground. 
They  may  be  diverted  into  suitable  receiving  apparatus  by 
the  s^'mple  arrangement  shown  in  the  accompanying  il- 
lustr^  'ion.     However,  even  when  they  are  diverted  in  this 


18 


RADIO  FOR  EVERYBODY 


manner,  they  are  of  frequencies  of  the  order  of  several 
thousand  cycles,  and  will  not  produce  any  sounds  in  the 
usual  telephone  receiver  because  they  are  beyond  the 
range  of  audibility.  But  remember,  the  waves  are  in 
trains  or  groups.  By  making  use  of  a  device  that  can 
convert  these  trains  or  groups  into  direct  current — current 
flowing  in  only  one  direction,  we  secure  a  series  of  im- 
pulses flowing  in  one  direction.  The  device  which  accom- 
plishes this  purpose  is  known  as  the  detector.  The  current 
flowing  through  the  telephone  receiver  is  smoothed  out 
into  single  impulses  of  a  frequency  corresponding  to  the 


An+enna 


Ground 


The  essentials    of   receiving    radio    signals,   comprising    tiie  an- 
tenna, inductance   coil  for  tuning,  crystal  detector,  telepliones, 
and   tlie   ground. 

speed  of  the  vibrator  or  current  supply  at  the  transmit- 
ting end.  Thus  the  diaphragm  of  the  telephone  is  actu- 
ated at  an  audible  frequency. 

In  the  case  of  undamped  waves,  which  are  produced  in 
a  different  manner  and  received  by  more  elaborate  re- 
ceiving equipment,  it  is  also  necessary  to  bring  the  inter- 
cepted waves  down  to  audibility.  In  the  reception  of  con- 
tinuous wave  radio  telephony,  however,  the  waves  are 
modulated  or  altered  by  the  impressed  telephonic  char- 
acteristics, and  while  the  receiver  may  not  make  the  actual 


RADIO  FOR  EVERYBODY  19 

waves  themselves  audible  because  of  their  high  frequen- 
cies, it  does  make  audible  the  fluctuating  potential  of  the 
waves  and  reproduces  the  sounds  uttered  at  the  trans- 
mitter. In  other  words,  it  does  not  concern  itself  with 
the  carrier  waves,  but  only  with  the  sounds  carried. 

Fitting  the  Radio  Apparatus  to  the  Task  in  Hand 

In  entering  upon  radio  as  a  hobby,  the  beginner  is 
confronted  with  a  question  of  choice  of  apparatus.  Thus 
he  can  buy  the  parts  and  build  his  own  receiving  set  and 
transmitter;  he  can  buy  the  separate  pieces  of  apparatus, 


Diagrammatic  explanation  of  why  a  "detector  detects  radio 
waves.  Tlie  liigh  frequency  current  produced  by  tlie  inter- 
cepted wave  is  shown  in  the  upper  half  of  the  diagram,  Tvhile 
the  lower  half  shows  how  the  detector,  being  a  one-way 
conductor,  only  permits  half  the  current  to  flow^  through, 
therefore  making  it  a  direct  current,  which  affects  the  tele- 
phone reeiver.  Certain  factors  cause  the  individual  pulsations 
of  a  wave  train  or  group  to  slur  into  one  note  in  the  tele- 
phone receiver.  Therefore,  there  is  one  sound  for  each  train 
or  group  of  waves. 

all  finished  and  ready  to  be  connected  with  other  instru- 
ments so  as  to  form  a  complete  set ;  or  he  can  buy  a  com- 
plete receiving  set  and  sending  set,  all  wired,  ready  to  be 
used.  Latterly,  because  of  the  popular  interest  in  radio, 
there  have  appeared  various  types  of  phonograph-like 
receiving  sets,  in  which  the  radio  mechanism  is  so  simple 
that  virtually  no  knowledge  of  radio  is  required. 

If   the  layman   is   only   interested   in   receiving   radio- 
phone service,  and  does  not  care  to  be  troubled  with  even 


20  RADIO  FOR  EVERYBODY 

an  elementary  knowledge  of  radio,  then  by  all  means  the 
simplest  type  of  apparatus  is  urged.  In  that  event  it  is 
well  to  purchase  a  complete  receiving  set,  already  wired, 
as  self-contained  as  possible,  which  only  needs  to  be  con- 
nected to  the  aerial  and  ground  for  immediate  results. 

If  the  layman  wishes  to  do  a  little  experimenting  and 
little  by  little  master  the  details  of  radio  communication, 
then  it  may  be  well  for  him  to  purchase  separate  radio 
units,  each  one  finished  but  so  arranged  as  to  permit  its 
use  with  other  units  for  all  kinds  of  purposes. 

Finally,  if  the  layman  wishes  to  build  his  own  receiving 
set  not  only  because  of  the  experience  gained  but  also 
on  the  grounds  of  economy,  then  the  various  parts  can 


A    simple    receiving    set,    consisting    of   a    variable    inductance,   a 
crystal  detector,   and  a  pair  of  telephones.      Such  a  set   will  re- 
ceive radiophone  concerts  over  25  miles   and   perhaps  more  with 
good  conditions  obtaining. 

be  purchased  and  assembled.  Some  manufacturers  today 
offer  all  the  parts  for  a  complete  receiving  set,  thus  facili- 
tating work  of  this  kind. 

For  transmitting  work,  the  same  applies.  However,  it 
is  well  to  say  here  that  transmitting  is  something  quite 
different   from   receiving.     Anyone   can  receive,   without 


RADIO  FOR  EVERYBODY  21 

licenses  or  other  formality ;  but  one  must  obtain  licenses 
for  transmitting.  The  transmitting  station  must  be 
licensed  by  the  Department  of  Commerce,  as  explained  in 
another  chapter,  and  the  operator  of  such  a  station  must 
pass  an  examination  in  sending  and  receiving  in  order 
to  obtain  an  operator's  license,  without  which  one  is  barred 
from  transmitting  work.  So,  all  in  all,  the  layman  had 
best  confine  his  efforts  to  receiving  only  until  some  subse- 
quent time  when  he  can  afford  to  put  in  the  necessary 
time  to  master  the  various  details  of  radio  in  order  to 
pass  the  Government  test  and  obtain  his  operator's  license. 

The  growth  of  radio-phone  broadcasting  has  created 
a  demand  for  simple  receiving  sets  with  the  minimum  of 
controls  and  adjustments.  Thus  there  have  appeared  re- 
ceiving sets  made  in  the  form  of  phonographs  which  repre- 
sent an  effort  to  cater  to  the  desires  of  persons  who  want 
the  radio-phone  service  with  all  the  radio  left  out,  so 
to  speak.  These  sets  must  be  developed  to  a  high  state 
of  perfection  in  short  order,  but  for  the  present  they 
must  be  looked  upon  as  being  somewhat  premature  at- 
tempts. In  fact,  much  of  the  receiving  apparatus  which  is 
now  on  the  market  is  designed  for  radio  communication 
work  rather  than  for  radio-phone  broadcasting  work,  and 
this  applies  particularly  to  those  sets  making  use  of  large 
horns  for  throwing  the  sound  out  into  a  room,  in  place 
of  the  head  'phones.  The  time  must  come  when  such 
sets  will  be  designed  with  special  attention  given  to  the 
acoustical  properties  of  the  various  components,  just  as 
the  better  types  of  phonographs  have  been  consistently 
developed  through  unceasing  experimentation  and  re- 
search until  they  have  been  taken  out  of  the  talking  ma- 
chine class. 

For  short  ranges,  inexpensive  radio  receiving  sets  can 
be  obtained.  There  are  sets  selling  as  low  as  $15.00, 
which  give  passable  results  with  the  broadcasting  station 
but  ten  miles  or  so  away.  For  $25.00  there  are  several 
receiving  sets  available  which  give  good  reception  of 
radio-phone  service  up  to  25  miles  or  more.     These  sets 


23 


RADIO  FOR  EVERY/BODY 


are  quite  simple,  having  only  one  or  two  controls  for 
varing  the  wave  length,  and  a  simple  detector  of  the  so- 
called  crystal  type.  Such  a  detector,  as  will  be  explained 
further  on  in  the  chapter  dealing  with  receiving  appara- 
tus, requires  no  battery  current. 

Stepping  beyond  the  25-mile  range,  we  come  to  the  bet- 
ter kinds  of  receiving  sets  with  more  elaborate  tuning 
devices  and  the  so-called  vacuum  tube  detector.  This 
detector,  unlike  the  simple  crystal  detector,  requires  two 


The  interchangeable  panel  idea  is  quite  popular  at  present.  ICach 
component  of  a  receiving  set  is  mounted  on  a  standardized 
panel,  and  as  many  panels  as  are  desired  can  be  used  at  one 
time  with  or  without  cabinets.  The  idea  is  quite  similar  to  the 
sectional    bookcase,    which    grows    with    one's    needs. 


batteries  for  its  operation.  It  must  have  a  low-voltage 
battery,  giving  from  1>4  to  6  volts,  depending  on  the 
type  employed,  and  a  high-voltage  battery  giving  from 
15  to  22 >4  volts.     The  low- voltage  battery  is  known  as 


RADIO  FOR  EVERYBODY  23 

A  or  filament  battery,  because  it  operates  the  filament  just 
as  in  the  case  of  an  ordinary  electric  light,  while  the 
B  battery  or  plate  battery  has  to  do  with  the  intricate 
workings  of  the  tube.  In  one  type  of  receiving  set  sell- 
ing for  $75.00,  and  quite  effective  for  ranges  up  to  75 
miles,  a  special  1^-volt  tube  is  employed  which  can  be 
operated  on  a  single  dry  cell.  Otherwise,  the  usual  vacuum 
tube  requires  a  storage  battery  because  it  draws  over 
one  ampere  of  current  at  a  voltage  of  6. 

Passing  on  to  ranges  over  100  miles,  a  still  better 
set  is  required.  We  now  reach  a  point  where  radio 
begins  to  cost  real  money.  Figuring  on  the  basis  of 
$1.00  per  mile,  which  is  the  figure  generally  quoted  by 
conservative  radio  men,  we  come  to  sets  of  elaborate 
design  costing  upwards  of  $100.00,  with  numerous  ac- 
cessories bringing  the  total  cost  up  to  $200  and  $300. 
These  sets  are  generally  used  in  connection  with  what  is 
known  as  an  amplifier,  which  is  a  device  for  building  up 
the  weak  signals  or  music  or  talk.  The  amplifier  may 
be  obtained  in  the  one-step,  in  the  two-step,  or  in  the 
three-step  models.  Generally,  the  two-step  model  is  em- 
ployed, for  the  reason  that  it  gives  an  amplification  of 
several  hundred  times  the  original  signal  strength,  and 
does  not  cause  too  many  foreign  noises.  Amplifiers  make 
use  of  vacuum  tubes,  which  in  general  appearance  are 
very  much  like  the  detector  tubes.  They  differ  only  in 
the  vacuum  content  of  the  tube.  Since  the  amplifiers 
magnify  all  sounds  and  irregularities  in  a  circuit  of  which 
they  form  part,  it  stands  to  reason  that  everything  is 
amplified  together.  For  this  reason  the  amplifier  should 
only  be  used  when  the  signal  strength  is  quite  low  and 
must  be  increased  for  proper  reception.  Furthermore, 
amplifiers  must  be  used  in  connection  with  loud-speaking 
telephones.  It  is  often  necessary  to  use  the  usual  two-step 
amplifier,  and  then  a  separate  amplifier  for  the  loud- 
speaker when  extremely  loud  music  or  talk  is  required 
for  a  large  hall. 

At  this  point  it  becomes  necessary  to  study  the  various 


24  RADIO  FOR  EVERYBODY 

terms  encountered  in  radio  work,  as  well  as  the  accom- 
panying diagram  giving  the  various  symbols  showing  how 
the  different  pieces  of  apparatus  are  designated  in  the 
wiring  diagrams  that  follow.  The  author  had  wished  to 
avoid  all  wiring  diagrams,  but  found  that  there  was  no 
other  manner  in  which  specific  information  concerning 
the  arrangement  of  radio  apparatus,  could  be  given. 
Simple  transmitting  and  receiving  sets  could  be  shown  in 
more  pictorial  form,  but  when  the  more  advanced  equip- 
ment is  to  be  shown  we  must  resort  to  the  conventional 
wiring  diagrams.  However,  a  little  attention  given  to 
these  symbols  will  enable  even  the  layman  to  master  the 
art  of  reading  a  radio  wiring  diagram,  and  he  then  be- 
comes competent  to  read  any  wiring  diagram  to  his  very 
substantial  benefit. 

The  most  common  terms  employed  in  everyday  radio 
work  are  as   follows : 

Aerial — ^One  or  more  wires  insulated  from  and  sus- 
pended at  a  certain  height  above  the  ground  and 
used  to  radiate  energy  in  the  form  of  electric-mag- 
netic waves  produced  by  a  transmitter.  When  used 
for  receiving  purposes,  the  correct  name  is  antenna, 
though  both  terms  are  used  interchangeably  for 
either  reception  or  transmission. 

Alternating  Current,  (Abbreviated  A.  C.) — An  electrical 
current  whose  direction  of  flow  is  constantly  chang- 
ing during  a  period  of  time.  Thus,  when  we  speak  of 
a  60-cycle  alternating  current,  we  mean  one  that  com- 
pletely reverses  its  direction  of  flow  sixty  times  per 
second.  Alternating  current  plays  a  prominent  part 
in  many  phases  of  the  radio  art. 

Ammeter — An  instrument  used  for  measuring  the  flow 
of  current  in  amperes  through  a  given  circuit.  Ai 
ammeter  is  invariably  connected  in  series  with  a 
given  circuit,  so  that  the  current  has  to  flow  through 
it.  Sometimes,  the  current  is  passed  through  a  heavy 
conductor  placed  across  the  ammeter  proper,  such  a 


Aliernator 

Ammeter 
Aerial 
Arc 
Batferu 


Bu 


zz&r 


T-t 
1 

— i|.|.|.|,|.l.|.h- 


Condenser      — ]  | —  or  -l^j_ 

Variable  Condenser  -4^ 

Connection  of  wires      — \— 


No  connection  — p — 

Coupled  coils  §  e 

Variable  couplina        WW 

Detector  — }< — 

Galvanometer  "(G)— 

Gap,  plain  «  « 

Gap,  cjuenched      llllll 

Generator.  D. C-  O 

(c)rou*^ci  ■==■     |i|i|i|i'| 


Grid  leak  and  J^TL 

Condenser 

Inductance  -^vwnn— 

Variable  Inductance      or 

Resistance  — ww* — 

Variable  resistance  — ww^ 

Single  pole       ^^^ 
Switches  Single throw"^ 

Single  pole  _^.^^   ^_ 

Double  throw 

Double  pole  ^^^;"— 

Single,  throw  ~^ 

Double  pole  __'>v>.   __ 

Double  throw         — "^   — 

Reversing  I^^^^C 

Telepkone  Receiver  florc^^ 
Telephone  Tronsmitter    i(Jj 


Tra  n  sf o  r  m  e  r    1 Q  i_ 
Vacuum  Tube 
Variometer 
Voltmeter 


-<v>- 


standard    symbols    used   in   radio    wiring    diagrams.      These    symbols 

should  be  mastered  so  that  the  radio  devotee  can  understand  wiring 

diagrams   and   follow    out   their   instructions. 


26  RADIO  FOR  EVERYBODY 

conductor   is   known   as   a   shunt,    and   permits    of 
handling  heavy  currents. 

Ampere — The   standard   electrical   unit   of   current   flow. 

Amplifier — This  term  is  used  in  referring  to  either  an 
amplifier  tube  or  an  amplifier  receiving  unit.  It  is 
the  device  which  builds  up  or  magnifies  the  waves 
or  sounds  in  a  radio  receiving  set.  (See  vacuum 
tube.) 

Amplitude — In  radio  work,  this  refers  to  the  highest 
point  reached  by  a  wave  or  oscillation,  i.  e.,  the  crest 
of  each  wave.  A  wave  may,  therefore,  have  a  high  or 
low  amplitude  according  to  the  initial  energy  which 
created  it. 

Antenna — See  aerial. 

Armstrong  Circuit — See  Regenerative  Circuit. 

Atmospherics — Also  known  as  static,  strays,  X's.  "The 
noises  of  space."  Natural  electrical  discharges  oc- 
curring in  the  ether  and  in  reality  miniature  lightning 
storms.  Since  these  discharges  travel  through  the 
same  medium  as  radio  waves,  they  are  readily  picked 
up  by  receivers  and  prove  very  troublesome  at  times. 
It  is  comparatively  difficult  to  tune  out  these  dis 
turbances  for  they  have  no  definite  wave  length. 

Audio  Frequencies — Frequencies  corresponding  to  vibra- 
tions which  are  normally  audible  to  the  human  ear. 
All  frequencies  below  10,000  cycles  per  second  are 
termed  audio  frequencies.     (See  radio  frequencies.) 

B  Battery — The  battery  used  for  supplying  the  plate 
current  for  the  vacuum  tube.  This  battery  generally 
runs  from  15  volts  to  22^^  volts. 

Broadcasting — As  applied  to  radio  work,  this  stands  for 
the  simultaneous  sending  of  intelligence  either  by 
radio  telegraphy  or  telephony  from  a  given  central 
point  for  the  benefit  of  a  great  number  of  receiving 
stations  located  within  the  broadcasting  station's 
range. 

Capacity,  (abbreviated  C) — Capacity  as  used  in  radio 
work  plays  a  very  important  part.     The  unit  of  elec- 


RADIO  FOR  EVERYBODY 


2t 


trical  capacity  is  the  Farad,  but  the  farad  being  too 
large  for  practical  radio  work,  the  micro-farad  (ab- 
breviated m.  f.  d. — one  millionth  of  a  farad)  is  used. 
Thus  we  speak  of  a  receiving  or  transmitting  con- 
denser having  a  capacity  of  .001  mfd,  or  one  thou- 
sandth part  of  a  microfarad. 
Cascade  Amplification — This  refers  to  high  amplification 
of  received  radio  signals,  wherein  several  vacuum 
tubes  are  employed  in  cascade  fashion  which  means 
that  one  amplifies  the  sounds  or  waves  and  passes 


ANTENiNA    LEAD 


^^k.'-.'^  ,  •-.-^ 


^       ■      TUNiNG  COIL. 

i^i    yr  8Af?E:    WtRE,    WlNOlNe 


CRYSTAL    DETECTOR 


TUNING   cost,   St-iDER 


Receiving:   set   of    simple   construction,   making   use   of   a   tuning: 

coil  with  single  slider,  a  crystal  detector,  and  a  single  telephone 

receiver.      This    set    may    be   used    for    short    distances. 

them  on  to  another,  which  amplifies  the  sounds  and 
passes  them  on  to  another,  and   so  on.     Thus,   we 
may  speak  of  a  three-step   (cascade)   amplifier. 
Choke  Coil — A  coil  wound  to  have  great  self-induction  or 
choking  efifect  when  in  the  path  of  alternating  cur- 


28  RADIO  FOR  EVERYBODY 

rent.  Choking  action  when  introduced  in  a  radio  cir- 
cuit is  called  impedance. 

Circuit — In  radio  and  electrical  work  the  path  in  which  an 
electric  current  flows  is  called  a  circuit.  A  circuit 
may  be  open  or  closed  or  oscillating. 

Close  Coupling — A  tuning  coil,  set  of  coils,  or  a  trans- 
former is  saiid  to  be  close-coupled  when  the  primary 
and  the  secondary  are  very  close  together,  thereby 
causing  much  mutual  inductance.  Coupling  permits 
of  the  transference  of  energy  from  one  circuit  to  an- 
other. Therefore,  the  closer  the  coupling,  the  greater 
the  transference  of  energy  and  the  interplay  of  the 
circuits.  The  primary  of  any  coupler  or  transformer 
device  is  the  winding  which  carries  the  initial  cur- 
rent; the  secondary  is  the  winding  which  receives  its 
current  from  the  primary.  In  a  coupler  the  primary 
is  connected  to  antenna  and  ground,  and  the  second- 
ary is  connected  with  the  detector  circuit. 

Condenser — Two  or  more  sheets  of  metal  separated  by 
an  insulator  called  the  dielectric.  A  condenser  is 
used  in  radio  work  for  collecting  electrical  energy, 
and  for  bringing  circuits  into  tune  or  resonance. 

Counterpoise — One  or  more  wires  stretched  immediately 
above  the  earth,  but  insulated  from  the  earth.  The 
counterpoise  wires  are  usually  directly  beneath  the 
regular  aerial.  This  device  is  employed  in  trans- 
mission and  reception  when  a  good  ground  connection 
is  not  available.  The  counterpoise  is  used  in  aircraft 
radios,  where  a  ground  connection  would  be  out  of 
the  question.  It  is  also  used  extensively  in  continu- 
ous wave  transmission. 

Continuous  Wave,  (Abbreviated  C.  W.)^ — A  form  of  elec- 
tro-magnetic wave  used  extensively  in  radio  work. 
C.  W.  waves  have  a  constant  amplitude  and  by  the 
same  sign  no  damping  effect,  as  distinguished  from 
the  older  form  of  discontinuous  waves  which  are  soon 
damped  out.  C.  W.  makes  possible  long-distance 
amateur  radio  telegraphy,  as  well  as  radio  telephony. 


RADIO  FOR  EVERYBODY 


29 


Coupler — A  device  for  transferring  radio  energy  from 
one  circuit  to  another.  Ordinarily,  the  primary 
winding  of  the  coupler  is  connected  with  the  antenna 


VI       ^^^^^^H^Hn 

1 

-^ .  b  r  5  "~^"''<v--.^|HHHHHh 

EHIBraniV 

''L>N!\G  " -^ Mg- '^|ij|ili||iHM{WiBiBltB^ 

K3"3^V 

AND  w-^r  ,  .1  '^l^fl^BBHlBBllillii^^ 

Hfi^^^K, 

Tjs-'  ''-~-^j|BpWMWwyi!!!WmliHli*«<»^^ 

I^HsiBMk 

1         iBHBMllliWi'             iii'iii Ill I'll' 

B^^g^ 

^^^^^^B^^^m  ^~-^^^^^H 

B^HWi|^ 

^■H^^^^^PIP.^'?^  ^»M«^ 

I^^M*** 

-^'-'^S 

B|^H[^H^^^^^>^|^g 

1,'v-    iSE 

^KBB^^maB<iiy!&rs>!^,^'  ^.^T^FSB-^  i. 

W^lwi^A^^WS' 

1    tv'^B 

W^Sl^^^^^^^^^^m^l-       ■ 

as-M 

M^S^^^B^^^^^^m 

m^^'t^^m-  ■ 

HH^^^^I^^^^^V^'^^.w.w'Mm^  ..I'!-. 

k»«Ms»-;s'»^M 

hH'^' 

^Wr^^^^™"-^'  •%^:^5 

~-~«,'~;,a&So,.,*!a.  '*™ 

H/«=^K 

""'"^^ 

V|        record'  A^S'JMS 

1 

Receiving:  set  made  in  the  form  of  a  plionograph;  in  fact;  this 
cabinet  may  be  used  as  a  phonogrraph  or  radio  telephone  receiv- 
ing- set  at  will.     The  radio  set  makes  use  of  the  phonograph  horn. 

and  ground,  and  the  secondary  with  the  detector 
circuit.  Couplers  are  of  several  different  types,  such 
as  the  loose-coupler  and  vario-coupler. 
Crystal  Detector — ^^Certain  metallic  crystals  when  intro- 
duced in  a  radio  receiving  circuit  have  the  property 
of  rectifying  the  incoming  signal  oscillations,  which 


30  RADIO  FOR  EVERYBODY 

are  high  frequency  alternating  currents,  into  direct 
current,  so  that  the  resultant  intermittent  direct  cur- 
rent will  work  a  sensitive  telephone  receiver. 

Detector — Any  apparatus  which  transforms  the  oscilla- 
tions received  by  the  antenna  into  visible  or  audible 
indications. 

Direct  Current,  (abbreviated  D.  C.) — An  electric  current 
flowing  continuously  in  one  direction.  In  a  two-wire 
circuit,  for  example,  direct  current  always  flows 
from  the  positive  source  to  the  negative  return. 
Therefore,  direct  current  always  has  a  readily  de- 
terminable polarity,  while  alternating  current  (A.  C), 
which  is  constantly  reversing  its  polarity  while  flow- 
ing through  a  circuit,  has  no  apparent  polarity. 

Electron — The  ultimate  particle  of  negative  electricity, 
which  plays  a  fundamental  part  in  the  constitution 
of  matter  as  well  as  in  the  electric  current.  Radio- 
active emanations,  electric  discharges,  etc.,  consist  of 
streams  of  electrons,  ejected  at  immense  velocities 
from  the  atoms  of  which  they  formed  part;  and 
ordinary  electric  currents  are  in  some  way  an  elec- 
tronic phenomenon. 

E.  M.  F. — Electromotive  force  or  electrical  pressure  or 
potential,  the  unit  of  which  is  the  volt. 

Ether — A  hypothetical  medium  of  great  elasticity  and 
extreme  minuteness,  supposed  to  pervade  all  space  as 
well  as  the  interior  of  solid  bodies.  It  is  the  medium 
through  which  light,  heat  and  radio  waves  have  here- 
tofore been  said  to  be  transmitted.  The  Einstein 
theories  have  shattered  the  ether  theory  for  the 
moment,  however,  although  many  radio  men  still  cling 
to  it  in  explaining  radio  transmission. 

Flat-Top  Aerial  —  One  whose  suspended  wires  are 
stretched  parallel  to  the  earth. 

Frequency — In  alternating  currents,  the  rapid  reversal  of 
the  current  through  a  circuit.  Thus,  we  speak  of  a 
60-cycle  current  as  one  which  has  sixty  complete  re- 
versals per  second  or  a  frequency  of  60  cycles.     (See 


A  huge  radio  receiving  set  and  loud-speaker,  made  in  the  form  of 

huge  cabinet.     Such  a  receiving  set  gives  loud  enough  music  to  fill 

large  hall  or  motion  picture  theatre. 


32  RADIO  FOR  EVERYBODY 

Alternating  Current  and  Audio  and  Radio  Frequen- 
cies.) 

Grid  Leak — A  very  high,  non-inductive,  resistance  con- 
nected across  the  grid  condenser  or  between  the  grid 
and  the  filament  of  a  vacuum  tube  to  permit  exces- 
sive electrical  charges  to  leak  off  to  an  external 
source,  thus  furnishing  stable  control  under  all  opera- 
ting conditions. 

Ground,  (or  Earth  which  is  the  term  used  in  England)  — 
In  radio  work  the  ground  is  the  other  side  of  the 
wave  distributing  system.  It  functions  in  connection 
with  the  aerial  or  antenna  of  most  sending  and  receiv- 
ing systems  as  a  large  condenser.  The  term  "ground" 
is  used  for  any  connection  with  the  earth,  river  or 
sea.     (See  counterpoise.) 

Harmonics — In  radio,  harmonics  refer  to  the  incidental 
waves  mostly  noticeable  in  undamped  or  C.  W.  wave 
operation.  These  harmonics  differ  in  length  and  fre- 
quency to  the  true  and  original  operative  wave  of 
such  transmitters.  The  first  harmonic  is  three  times 
that  of  the  true  frequency,  or  one-third  the  wave 
length  of  the  aerial;  the  second  harmonic  is  five  times 
the  true  frequency  or  one-fifth  the  wave  length ;  the 
third  harmonic  is  seven  times  the  true  frequency  or 
one-seventh  the  wave  length.  At  times,  amateurs  will 
hear  the  harmonics  of  high  power  long  wave  stations 
while  their  tuners  are  set  for  much  shorter  waves. 
This  accounts  for  the  reception  of  a  radio-phone  sta- 
tion at  two  entirely  different  points  on  the  tuner  of 
the  receiving  set. 

Henry — The  unit  of  inductance. 

Hertzian  Waves — ^Electro-magnetic  waves  named  after 
the  discoverer,  Prof.  Heinrich  Hertz,  in  1887.  These 
waves  are  the  basis  of  radio  communication. 

Hook-up — A  diagram  showing  the  wiring  of  any  wireless 
receiving  or  transmitting  set.  Diagrams  of  this  kind 
make  use  of  certain  conventional  symbols  to  repre- 
sent the  various  pieces  of  apparatus. 


RADIO  FOR  EVERYBODY  33 

Hot  Wire  Ammeter — An  instrument  used  in  radio  trans- 
mission work  for  measuring  the  current  in  amperes 
by  means  of  a  wire  that  expands  in  proportion  to  the 
heat  generated  by  the  current  passing  through  it. 

Impedance — This  is  the  term  apphed  to  the  resistance 
offered  by  a  coil  of  wire  to  a  current  flowing  through 
it  due  to  the  counter-electromotive  pressure,  irre- 
spective of  the  actual  resistance  of  the  conductor  in 
ohms.  Counter-electromotive  pressure  is  developed 
in  certain  forms  of  inductance,  and  this  counteracts 
the  flow  of  current  to  a  greater  or  less  degree.  Impe- 
dance may  be  said  to  be  the  result  of  reactance. 

Inductance,  (abbreviated  L) — Inductance,  like  capacity, 
plays  a  very  prominent  part  in  radio  circuits.  It  is 
the  transfer  of  an  electric  or  magnetic  current  from 
an  electrified  or  magnified  body  to  a  non-electrified 
or  non-magnetized  body  by  close  proximity  but  with- 
out actual  contact.  The  unit  of  inductance  is  the 
Henry.  In  radio  work  the  mil-Henry  and  the 
micro-Henry  are  the  more  practical  terms  used. 

Insulator — A  non-conductive  material  through  which 
electricity  will  not  pass. 

Kilozmtt,  (abbreviated  K.  VV.) — One  thousand  watts,  a 
unit  used  in  measuring  large  amounts  of  electricity. 

Loop  Antenna — A  small  frame  wound  with  a  number  of 
turns  of  wire  used  in  reception  and  thus  eHminating 
both  outdoor  antenna  and  ground  connections. 

Loose-Coupler — (See  Coupler.) 

Loud-speaker — Any  receiving  device  designed  to  repro- 
duce signals  or  speech  loud  enough  to  be  heard  with- 
out the  use  of  the  conventional  telephone  receivers. 

Megohm — ^One  million  ohms. 

Microfarad,  (abbreviated  mfd.) — One  millionth  part  of 
a  Farad  and  the  practical  unit  of  capacity. 

Microphone — A  device  for  converting  sounds  into  elec- 
trical equivalents  in  a  given  circuit.  In  other  words, 
the  microphone  transfers  sounds  to  a  given  electrical 
circuit  by  causing  certain  variations  in  the  flow  of 


34  RADIO  FOR  EVERYiBODY 

electricity.  It  is  the  instrument  used  in  both  wire 
and  radio  telephony  to  transmit  speech,  and  generally 
consists  of  a  mass  of  loosely  packed  carbon  grains 
held  between  carbon  blocks,  and  subjected  to  vary- 
ing pressure  by  the  vibration  of  the  diaphragm. 

Milliampere,  (abbreviated  M.  A.) — The  thousandth  part 
of  one  ampere. 

Natural  Frequency — The  natural  wave  length  obtained 
with  any  aerial  or  circuit  without  the  introduction 
of  other  elements. 

Ohm — The  unit  of  electrical  resistance. 

Ohm's  Law — The  fundamental  law  of  electricity.  It  states 
that  the  current  in  amperes  flowing  through  a  cir- 
cuit is  equal  to  the  pressure  in  volts  divided  by  the 
resistance  in  Ohms. 

Oscillations — Alternating  currents  of  very  high  frequen- 
cies are  called  electrical  oscillations.  If  the  amplitude 
of  a  series  of  oscillations  is  constant,  the  oscillations 
give  rise  to  continuous  or  undamped  waves ;  but  if  the 
amplitude  is  not  constant  and  is  of  a  decaying  nature, 
as  in  the  spark  method  of  transmission,  we  obtain 
damped  waves. 

Potential — Term  applied  to  voltage  or  electrical  pressure. 
(See  EMF  and  Volt.) 

Radiation — The  transmission  of  energy  through  space  in 
the  form  of  electro-magnetic  waves.  By  the  radiation 
of  a  transmitter  is  meant  the  volume  of  high  fre- 
quency current  which  is  being  delivered  to  the  aerial 
for  propagation  in  the  form  of  waves. 

Radio  Frequencies — Frequencies  corresponding  to  vibra- 
tions not  normally  audible  to  the  human  ear.  All 
frequencies  above  10,000  cycles  per  second  are  termed 
radio  frequencies.     (See  Audio  Frequencies.) 

Reactance — See  Impedance. 

Rectifier — An  apparatus  which  converts  alternating  cur- 
rent (A.  C.)  into  pulses  of  direct  current  (D.  C.) 
Tungar,  Rectigon  and  Kenetron  apparatus  are  em- 
ployed   for    rectifying    purposes.      Certain    metallic 


RADIO  FOR  EVERYBODY  36 

crystals  also  have  rectifying  action  when  used  as  de- 
tectors in  reception. 

Regenerative  Circuit,  (also  known  as  the  Armstrong  cir- 
cuit) a  radio  circuit  comprising  a  vacuum  tube  so 
connected  that  after  detection  and  rectification,  the 
signal  introduced  in  the  plate  circuit  is  led  back  to 
or  caused  to  react  upon  the  grid  circuit,  thereby  'in- 
creasing the  original  energy  of  the  signal  received  by 
the  grid  and  greatly  amplifying  the  response  to  weak 
signals.  In  reception,  the  leading  back  or  feeding 
back  of  plate  energy  to  the  grid  for  further  strength- 
ening is  usually  accomplished  by  means  of  a  small 
coil  placed  close  to  the  secondary  of  the  receiving 
tuner.  This  small  coil  is  frequently  called  the 
''tickler." 

Resistance — 'Opposition  to  the  flow  of  an  electric  current 
through  a  conducting  medium.  All  metals  have  more 
or  less  electrical  resistance.  Copper  is  used  univer- 
sally for  both  electrical  and  radio  work  on  account 
of  its  low  resistance,  comparatively  low  cost  and 
ready  supply.  Silver  is  a  better  conductor,  but  it  is 
too  expensive.     The  unit  of  resistance  is  the  Ohm. 

Resonance — A  very  important  function  of  radio  circuits. 
Resonance  in  a  given  circuit  is  said  to  exiist  when 
its  natural  frequency  has  the  same  value  as  the  fre- 
quency of  the  alternating  electromotive  force  intro- 
duced in  it.  The  current  is  then  in  tune  with  the 
natural  period  of  vibration  of  the  circuit.  The 
theory  of  electrical  resonance  is  the  same  as  that  of 
acoustics,  readily  demonstrated  by  the  tuning  forks, 
where  one  tuning  fork  will  not  respond  to  another 
unless  it  is  of  the  same  key  or  pitch.  Bringing  a  cir- 
cuit into  resonance  means  bringing  it  into  tune  with 
another  circuit  or  transmitter. 

Rheostat — ^A  variable  resistance  usually  employed  to  con- 
trol or  regulate  current  flow. 

Selectivity — In  radio  work,  the  ability  to  select  any  par- 


36  RADIO  FOR  EVERYBODY 

ticular  wave  length  to  the  exclusion  of  others ;  the 
fineness  of  tuning,  in  other  words. 

Sharp  Timing — Where  a  very  slight  change  of  a  tuner  or 
tuning  system  will  produce  a  marked  effect  in  the 
strength  of  signals.  The  sharper  the  tuning,  the 
greater  the  selectivity. 

Storage  Battery — Battery  which  can  be  recharged  at  inter- 
vals whenever  it  is  run  down;  a  storage  battery  is 
employed  to  supply  .current  for  operating  vacuum  tube 
filaments. 

Static,  (See  Atmospherics) — Disturbances  of  an  electrical 
nature  which  are  created  by  natural  causes  and  which 
interfere  materially  with  radio  work.  When  static 
is  exceptionally  bad  it  may  be  impossible  to  receive 
radio  telegraph  signals  or  radio-phone  service  through 
the  heavy  crashes  and  frying  sound  of  the  static. 

Transformer — Any  device  used  in  electrical  and  radio 
work  for  the  transference  of  energ}^  from  one  circuit 
to  another,  with  or  without  a  change  in  the  voltage  as 
desired.  Thus  we  have  Power  Transformers,  Am- 
plifying Transformers,  Telephone  Transformers,  Os- 
cillation Transformers,  Tuning  Transformers,  etc. 
All  transformers  have  a  primary  and  a  secondary 
winding.  The  primary  winding  receives  the  initial 
current,  which  it  passes  on  to  the  secondary  winding, 
with  the  same  voltage,  a  higher  voltage,  or  a  lower 
voltage,  according  to  the  ratio  which  the  primary 
and   secondary  windings  bear  to   one  another. 

Tuning — The  act  of  altering  capacity  or  inductive  values 
or  both  in  a  radio  circuit  so  as  to  bring  the  circuit 
into  resonance  with  an  external  source  of  similar 
character.  In  radio  receiving,  the  greatest  signal 
strength  is  possible  only  when  the  combined  induc- 
tance and  capacity  values  of  the  receiver  match  those 
of  the  transmitter. 

Undamped — A  train  of  high  frequency  oscillations  of 
constant  amplitude  such  as  continuous  waves  or  C.  W. 

Vacuum  Tube,  (abbreviated  V.  T.) — In  radio  work  this 


RADIO  FOR  EVERYBODY  37 

term  is  applied  to  a  glass  tube  exhausted  of  air  and 
containing  essentially  a  filament  for  the  creation  of 
electrons ;  a  plate,  positively  charged,  to  which  the 
electrons  are  attracted ;  and  a  grid,  consisting  of  a 
helix  of  fine  wire,  inserted  between  the  filament  and 
the  plate,  for  controlling  the  amount  of  electronic 
flow.  This  action  of  the  vacuum  tube  plays  three 
leading  functions  in  radio  work,  namely,  detection, 
amplification,  and  generation  of  high-frequency  elec- 
tro-magnetic waves. 
Vario-Coiipler — (See  Coupler. ) 

Variometer — An  instrument  which  serves  to  vary  the  in- 
ductance and  wave  length  value  of  any  circuit  in 
which  it  may  be  used.  It  consists  of  a  set  of  fixed 
windings  and  a  set  of  movable  windings,  the  latter 
being  rotated  on  twin  axis  in  the  usual  construction. 
When  both  sets  of  coils  carry  the  current  flow  in  the 
same  direction,  the  variometer  has  the  maximum 
inductance  value  or  wave  length.  When  the  coils 
are  turned  around  so  that  the  current  flow  in  both 
sets  of  coils  is  in  opposite  directions,  the  coils  are 
said  to  be  ''bucking"  each  other  and  the  inductance 
and  wave  length  value  are  at  a  minimum. 
Velocity  of  Waves — Radio,  electricity  and  light  waves 
travel  through  space  at  the  speed  of  186,000  miles  per 
second,  or  300,000  meters  per  second. 
J^olt,  (abbreviated  V.) — The  unit  of  electric  pressure. 
Voltmeter — An  instrument  for  measuring  the  voltage  of  a 

current  flowing  through  an  electric  circuit. 
JVaff,  (abbreviated  W.) — The  unit  of  electric  power.  To 
find  power  in  Watts  multiply  voltage  by  amperage. 
746  Watts  equals  one  horsepower.  1,000  Watts 
equals  one  kilowatt  (K.  W.) 
Wave  Length — Radio  waves  in  their  passage  through  the 
ether,  travel  in  undulating  wave  form  sim/ilar  to  the 
waves  at  a  seashore.  When  the  wind  is  blowing  hard 
and  steady  the  distance  between  each  wave  crest  is 
comparatively  long  while  if  the  wind  is  blowing  more 


38  RADIO  FOR  EVERYBODY 

mildly  and  in  short  spurts,  the  distance  between  wave 
crests  is  accordingly  shorter  and  we  have  short  waves. 
In  radio,  substitute  the  wind  for  the  transmitter  and 
you  have  the  same  action,  so  to  speak.    Wave  length 
is,  therefore,  closely  related  to  frequency, '  i.  e.,  long 
wave    lengths    have    low    natural    frequencies    while 
short  wave  lengths  have  greater  natural  frequencies. 
In  general,  short  wave  lengths   are  used   for   short 
distance  low-power  work,  while  long  wave  lengths  are 
employed  for  long-distance,  high-power  work. 
The  foregoing  list  by  no  means  covers  all  the  terms 
which   will   be   encountered   in   radio,   but   it   covers   the 
more  common  and  perhaps  least  understood  terms  con- 
fronting the  layman  at  the  very  outset.    As  one  gets  along 
ever  so  little  in  the  radio  art,  one  accumulates  a  vocabu- 
lary of  radio  terms  quite  readily  and  with  no  effort. 

After  all,  radio  is  a  subject  which  one  soon  masters.  It 
is  relatively  simple  after  the  essentials  are  clearly  under- 
stood. Furthermore,  in  no  other  line  of  endeavor  will 
one  find  so  much  good  fellowship  and  so  many  oppor- 
tunities of  receiving  a  helping  hand.  In  all  parts  of  the 
country  there  are  radio  amateurs  who  are  ever  ready  to 
extend  a  helping  hand  to  the  novice,  and  one  will  do  well 
to  get  in  touch  with  the  radio  amateurs  of  the  vicinity  at 
the  earliest  possible  moment.  They  are  the  greatest  asset 
the  novice  has  at  his  disposal.  Furthermore,  the  radio 
and  electrical  dealers  handling  radio  equipment  are  always 
ready  to  extend  all  possible  co-operation  and  information 
to  those  in  need  of  radio  aid.  It  is  part  of  their  service ; 
for,  in  purchasing  radio  apparatus,  one  is  seeking  a  definite 
service  rather  than  so  much  equipment. 

The  reader  is  advised  to  keep  in  touch  with  radio  devel- 
opments by  reading  the  various  periodicals  devoted  to  the 
subject,  as  v/ell  as  the  radio  sections  of  the  various  news- 
papers now  paying  special  attention  to  the  greatest  hobby 
of  the  age.  A  real  fund  of  valuable  information  can  be 
picked  up  in  this  manner,  especially  after  acquiring  the 
very  necessary  fundamentals  of  the  art,  the  imparting  of 
which  is  the  purpose  of  this  book. 


Chapter  II. 

RADIO-PHONE  BROADCASTING 
WHAT  IT  IS  AND  WHAT  IT 

MEANS 


^  ^  T  ADIES  and  gentlemen,  we  take  great  pleasure  in 
I  J  introducing  Mr.  Percy  Grainger,  the  famous 
pianist  and  composer,  who  will  entertain  us  this  evening 
with  several  of  his  favorite  pianoforte  selections.  After 
that,  please  stand  by  until  9.55  for  the  re-transmission  of 
the  Arlington  time  signals  " 

A  concert?  No.  A  vaudeville  performance?  Hardly. 
A  musicale  in  the  home  of  a  society  leader?  Not  this 
time. 

It  is  merely  a  bit  of  radio-phone  service  taken  at  ran- 
dom. Another  time  it  might  be  Mme.  Lydia  Lipkovska, 
court  singer  to  the  late  Czar  of  Russia,  or  Miss  Valentina 
Crispi,  violinist,  or  Miss  Sophie  Tucker,  famous  delin- 
eator of  darky  and  character  songs.  Again  it  might  be 
Governor  Edward  I.  Edwards  of  New  Jersey,  with  his 
latest  message,  or  Ed.  Wynn  and  the  entire  company  of 
"The  Perfect  Fool,"  representing  the  first  attempt  to 
broadcast  an  entire  theatrical  performance ;  or  Walter 
Camp,  foremost  authority  in  American  athletics. 

The  Radio  Voice  and  its  Audience 

Still  again,  at  a  different  hour  of  the  day,  it  may  be 
the  news  of  the  moment,  carefullv  selected  and  clearly 
heralded  word  by  word ;  marine  news,  weather  reports, 
children's    bedtime    stories,    health    talks,    business    talks, 


40  RADIO  FOR  EVERYBODY 

fashion  talks,  agricultural  reports,  Babson's  statistical 
service,  or  the  official  time  signals.  For  the  radio-phone 
service  is  unlimited  in  its  scope  of  subjects,  just  as  it  is 
virtually  unlimited  in  the  size  of  its  audience. 

But  what  is  the  radio-phone  service?  Where  is  it 
obtainable,  and  how?    What  does  it  cost?    Why  is  it  free? 

Typical  questions,  these,  at  a  time  when  radio  is  at  the 
height  of  popularity.  Only  a  short  while  back,  the  hobby 
of  radio  was  indulged  in  by  boys  and  voune^  men,  with 
occasionally  a  full-grown  man,  who,  perhaps,  were  more 
fascinated  by  the  technicalities  of  .the  radio  art  than  by 
the  actual  feat  of  communication  through  space.  Yet  it 
is  true  that  these  enthusiasts,  then  as  now,  were  carrying 
on  radio  conversations  among  themselves  by  means  of 
the  dot-and-dash  language  of  the  telegraph  code;  but  it 
was  certainly  evident  that  they  spent  a  goodly  part  of 
their  time  arranging  and  rearranging  their  radio  trans- 
mitters and  receivers  in  their  insatiable  ambition  to  span 
greater  distances. 

Then  came  the  radio-phone  service,  not  as  an  occasional 
thing  to  startle  the  radio  amateurs  already  engaged  in 
sending  and  listening  to  the  dot-dash  messages,  but  as  a 
regitlar  established  practice.  A  subsequent  development 
brought  about  a  definite  operating  schedule  and  a  pre- 
determined program,  so  that  now  the  person  with  a  radio 
receiving  set  knows  what  is  in  store  for  him  tonight,  to- 
morrow night,  or  even  next  Sunday  evening.  Radio- 
phone programs  are  printed  and  mailed  to  persons  on  the 
mailing  list  of  the  various  organizations  doino^  this  kind 
of  work. 

In  various  cities  throughout  the  country  there  are  radio- 
phone broadcasting  stations  now  in  operation,  which  send 
out  all  kinds  of  information,  talks,  and  music.  With  the 
proper  type  of  receiving  equipment  it  is  now  possible  for 
any  one  to  receive  the  raSio-phone  service  from  the  nearest 
station,  and,  if  there  are  several  stations  within  receiving 
range,  it  is  often  possible  to  receive  several  radio-phone 
services,  one  by  one,  with  absolute  selectivity,  although 
they  may  be  operating  simultaneously.     That  is  to  say. 


RADIO  FOR  EVERYBODY  41 

with  the  apparatus  properly  tuned,  one  station  may  be 
heard ;  then,  by  slightly  altering  the  tuning,  another  station 
may  be  picked  up,  and  so  on.  Further  tuning  may  pick 
up  an  amateur  radio-phone  transmitter  or  a  commercial 


The  radio-phone  receiving  set  finds  a  ready  place  in  every  pro- 
gressive home.  3Iany  an  hour  can  be  spent  listening  to  the 
musical  programs,  news  of  the  day,  weather  forecasts,  talks  by 
prominent    men,    and    other    radio-phone    broadcasting    features. 

Station  operating  or  "talking''  in  the  dot-dash-dot  language 
of  the  Continental  telegraph  code,  or  again  a  powerful 
transatlantic  station  transmitting  its  messages  at  an  ex- 
treme rate  of  speed,  thanks  to  automatic  transmitters  at 


42  RADIO  FOR  EVERYBODY 

one  end  and  the  photographic  or  phonographic  recorders 
at  the  receiving  end. 

Radio-phone  broadcasting  stations  are  sharply  tuned; 
in  fact,  all  radio-phone  transmitters  are  sharply  tuned ; 
for,  as  we  shall  learn  further  on,  this  is  one  of  the  cardinal 
points  in  favor  of  the  continuous  wave  transmitter,  which 
is  the  basis  of  the  radio-phone.  Thus  the  utmost  selec- 
tivity is  obtained  at  the  receiving  end,  and  interference  is 
reduced  to  a  minimum.  Indeed,  the  day  is  not  far  distant 
when  a  broadcasting  station  will  be  sending  various  serv- 
ices simultaneously,  ranging  all  the  way  from  a  sermon 
to  a  jazz  dance  piece,  and  from  a  talk  on  economics  to 
a  fashion  chat.  The  listener  wil!  merely  have  to  tune  his 
or  her  receiver  to  any  one  of  several  wave  lengths  in 
order  to  obtain  the  desired  service  at  that  time. 

Back  to  the  Humble  Beginning 
There  is  no  end  of  romance  in  the  story  of  the  radio- 
phone, radio  telephone,  or  wireless  telephone,  whichever 
you  please  to  call  it.  It  is  an  invention  that  came  back, 
so  to  speak,  in  a  big  way  after  an  ignominious  career. 
Such  a  wonderful  thing — this  idea  of  speaking  through 
space  without  wires,  cables,  tubes  or  other  physical  con- 
nections— was  almost  certain  to  fall  in  the  hands  of  un- 
scrupulous promoters,  long  before  the  serious,  honest  ex- 
perimenters had  had  a-n  opportunity  of  evolving  something 
more  than  a  crude,  laboratory  demonstration.  So  a  dozen 
years  ago  we  find  the  radio  telephone  nothing  more  than 
a  crude  device,  making  use  of  a  sputtering,  uncertain 
electric  arc  as  the  generator  of  the  high-frequency  energy. 
This  high-frequency  current,  so  uncertain  as  to  be  almost 
hopeless,  was  modulated  or  varied  by  means  of  some  form 
of  carbon  microphone.  This  instrument,  as  any  one 
familiar  with  its  construction  must  know  by  now,  is  quite 
unsuited  to  the  handling  of  heavy  currents.  It  consists 
of  little  more  than  a  mass  of  tiny  carbon  granules  held 
between  two  carbon  members.  The  passage  of  a  heavy 
current  through  such  a  mass  causes  the  carbon  granules  to 
fry  or  bake  because  of  the  heat  developed  through  the 
imperfect  contacts. 


44  RADIO  FOR  EVERYBODY 

It  was  the  good  fortune  of  the  author  to  participate  in 
wireless  telephony  back  in  1908  and  1909,  with  a  trans- 
mitter of  the  Telefunken  type  made  in  Germany.  A  series 
of  experiments  were  being  conducted  for  the  United  States 
Signal  Corps,  with  a  view  to  proving  the  practicability 
of  radio  telephony  in  military  communication.  The  dis- 
tance to  be  spanned  was  some  18  miles,  or  the  air  line 
between  Foi't  Hancock,  Sandy  Hook  and  Fort  Wood. 
Bedloes  Island,  in  the  very  shadow  of  the  Statue  of  Lib- 
erty overlooking  New  York  harbor.  The  high  hills  of 
Staten  Island  intervened,  making  communication  between 
the  two  points  all  the  more  difficult. 

For  the  transmitter  we  were  using  ten  electric  arcs, 
arranged  in  series  and  suppHed  with  a  550-volt  direct 
current.  Each  arc  consisted  of  a  copper  tank,  filled  with 
water,  and  a  large  carbon  button.  The  ten  arcs  were 
arranged  in  two  banks  of  five  arcs  each,  and  each  bank  was 
struck  or  started  at  the  same  time  by  pressing  a  single 
handle  controlling  five  arcs  at  a  time.  Three  sensitive 
ammeters  indicated  the  state  of  each  circuit — the  input 
circuit,  the  closed  oscillating  circuit,  and  the  antenna  cir- 
cuit. The  main  object  in  this  little  game  of  wireless 
telephony  was  to  get  the  three  circuits,  as  reported  by  the 
meters,  to  behave — and  what  a  job !  No  sooner  was  one 
circuit  tamed,  so  to  speak,  so  that  the  needle  of  its  meter 
remained  practically  stationary,  when  attention  would 
have  to  be  given  to  the  other  two  circuits  whose  meters 
were  playing  all  kinds  of  antics.  Then,  at  the  moment 
when  by  mere  chance  all  three  meters  were  more  or  less 
steady,  we  were  ready  to  talk. 

There  was  little  to  say,  because  if  we  were  heard  at  the 
receiving  end,  it  was  more  of  a  miracle  than  anything 
else.  So  we  simply  shouted  numbers  into  the  huge  horn 
connected  with  the  carbon  microphone— "One.  two,  three, 
four,"  and  so  on,  followed  by  "Fort  Wood,  Fort  Wood : 
how  do  you  get  me  now?  One,  tw^o,  three,  four,"  and 
so  on  again,  until  the  meters  began  their  antics  once  more. 
Occasionally  we  played  a  phonograph,  just  as  did  so  many 
other  radio  telephone  workers  in  the  pioneer  days. 


RADIO  FOR  EVERYBODY  45 

The  microphone  was  a  renewable  affair.  The  German 
builders  of  the  apparatus,  with  all  their  characteristic 
thoroughness  and  fine  workmanship,  made  the  microphone 
in  the  form  of  simple  cartridges  which  fitted  into  a  holder 
at  the  small  end  of  a  long  but  narrow  cardboard  horn. 
E^ch  mi'crophone  did  not  last  much  longer  than  five 
minutes  after  which  it  was  little  more  than  plain  junk. 
While  the  author  never  knew  the  exact  cost  of  these 
microphone  cartridges,  it  is  a.  safe  bet  that  they  cost  at 
least  $2.00  each.  Imagine  wasting  a  $2.00  microphone 
for  every  five  minutes  of  uncertain  telephonic  communi- 
cation ! 

Insurmountable   Obstacles   That   Were   Forgotten 

What  of  the  results?  Rotten,  absolutely  rotten!  In 
all  the  long  months  of  untiring  efforts  to  work  over  the 
short  eighteen-mile  span  between  Fort  Hancock  and  Fort 
Wood,  the  voice  and  the  phonographic  music  only  got 
through  a  half-dozen  times,  and  then  only  for  a  few  mo- 
ments so  that  odd  bits  of  conversation  or  music  were 
heard  by  the  Signal  Corps  officers  gathered  at  the  receiv- 
ing end. 

There  were  many  workers  engaged  in  solving  the  wire- 
less telephone  problem.  Most  of  them  used  the  arc  gen- 
erator, following  in  the  footsteps  of  the  Danish  scientist, 
Poulsen.  Some  used  high-frequen'cy  alternators,  but  the 
design  of  these  early  machines  was  such  as  to  give  a  low 
degree  of  efficiency.  Nothing  like  reliable  communication 
seemed  possible,  for  the  technical  obstacles  w^ere  far  too 
great  and  too  numerous. 

But  ail  the  while  certain  stock  promoters  were  reaping 
a  harvest.  To  them,  the  wireless  telephone  presented  an 
exceptional  opportunity.  The  ever-credulous  public  liked 
the  word  pictures  of  the  wireless  telephone  as  painted  by 
the  clever  stock  salesman.  The  story  of  the  Bell  telephone 
was  to  be  duplicated,  but  on  a  larger  scale ;  wireless  tele- 
phones were  to  be  installed  in  every  home ;  wires  and 
cables  were  to  be  done  away  with ;  every  one  would  carry 
a  wireless  telephone  about  in  one's  vest  pocket  or  hand- 


46  RADIO  FOR  EVERYBODY 

bag,  so  as  to  ensure  immediate  communication  with  any 
one  else,  and  so  on.  What  a  vivid  picture,  to  be  sure! 
Even  at  this  late  day,  with  the  marvelous  development  that 
has  taken  place  in  wireless  telephony,  such  a  picture  is 
quite  out  of  keeping  with  what  we  can  reasonably  expect 
for  decades  to  come.  In  fact,  so  long  as  the  present  sys- 
tem of  wireless  telephony  is  in  force,  it  is  doubtful  if  we 
can  ever  realize  all  the  remarkable  things  that  were  prom- 
ised to  the  gullible  stock  purchasers  of  but  a  decade  or 
more  ago. 

Of  course  there  were  proofs.  There  had  to  be  some- 
thing for  the  public  to  take  interest  in  this  latest  scientific 
development,  especially  to  the  extent  of  parting  with  so 
much  hard-earned  money.  Thus  there  was  a  demonstra- 
tion of  the  radio  telephone  between  two  of  our  cities. 
Everything  worked  to  perfection.  The  results  were  abso- 
lutely wonderful.  The  public  was  enchanted,  nothing  less  ; 
but  the  true  scientists  and  radio  workers  were  completely 
baffled.  Then,  when  certain  interests  were  closely  inves- 
tigated, an  unpaid  bill  for  the  leasing  of  a  telegraph  line 
between  said  two  cities  on  a  certain  date,  came  to  light. 
Needless  to  say,  the  date  corresponded  with  that  of  the 
successful  test  of  the  wireless  telephone.  The  inference 
is  obvious. 

Another  time,  it  was  a  German  company's  turn  to  make 
a  demonstration  for  the  German  army.  The  test  was  to 
be  bd:ween  Berlin  and  another  city  over  one  hundred  miles 
away.  Although  nothing  of  much  consequence  had  ever 
been  done  with  this  particular  German  wireless  telephone 
system,  on  this  occasion  it  worked  like  a  charm.  An  in- 
quisitive German  officer,  seeking  some  explanation  for  the 
sudden  upward  jump  in  the  radius  covered  by  the  wireless 
telephone,  not  to  forget  the  remarkable  clearness  and  loud- 
ness of  the  received  conversation,  suddenly  discovered  a 
telegraph  line  running  direct  between  the  transmitting 
station  and  the  receiving  station.  There  was  no  physical 
connection  between  the  two,  please  be  sure  to  note ;  but 
the  transmitting  aerial  was  parallel  to  and  but  a  short 
distance  away  from  the  telegraph  line  at  one  end,  while  the 


^t 


=  O  B 


%c. 


*       5* 

fll 


OSS 


lis 


IK^^^^^Mg 

r^^M 

f^~n 

M 

f'^  •- 

,s                   •         ^^^^^wi^ 

.:J 

'■liiilBiiililssM^^      ■ :  i!S?;?!lis;fc: :.: :.  :y5i'vi|ii;  ■  ii 

1    ■ /|j^ip 

Bp'''                                                                iiiiils-f'jis    >■  "^  W  ^^^^^wis-  "!*  * SSiiiiSftiB 

iilf  lifiyk:^,^  ^'-^''"^ 

■IWi^-^^^ 

-    .      "■"■*^ 

w\ 

%t'  .     ;       ,    ^ . ;  '^1' ■■ 

**^  ■ '■'    ^jft^^^S 

y:    ,    , 

;      "     .,  ;:^B|P^"''"''  ^  ri 

48  RADIO  FOR  EVERYBODY 

receiving  antenna  was  parallel  to  and  but  a  short  distance 
away  from  the  direct  telegraph  line  at  the  other  end.  As 
far  as  wireless  waves  are  concerned,  there  could  be  little 
gained  by  having  a  direct  connection.  It  was  scarcely 
more  than  straight  wire  telephony,  except  for  the  short 
jump  at  either  end.  In  fact,  this  form  of  wireless  tele- 
phony has,  strangely  enough,  come  to  be  used  during  the 
past  year  or  two  for  transmitting  telephone  messages  over 
high-power  transmission  lines.  It  is  also  used  in  wire 
work  in  a  somewhat  modified  form,  being  known  as  "wired 
wireless,"  as  will  be  explained  farther  on. 

When  a  Rival  Became  a  Partner 

And'  skipping  over  the  numerous  attempts  to  make 
something  out  of-  this  remarkable  laboratory  toy,  the  wire- 
less telephone,  we  come  to  the  time  when  the  American 
Telephone  and  Telegraph  Company  took  an  interest  in 
the  vacuum  tube  perfected  by  Lee  de  Forest,  as  is  explained 
elsewhere  in  this  work.  In  the  vacuum  tube  the  telephone 
engineers  realized  that  they  had  found  a  solution  to  many 
of  their  problems.  The  vacuum  tube  is  nothing  short  of 
an  electrical  acrobat;  it  can  do  all  sorts  of  tricks  which 
no  other  electrical  device  has  ever  been  able  to  perform. 
Thus  it  is  a  wonderful  alternating  current  generator ;  feed 
it  direct  current  and  it  gives  forth  alternating  current  of 
a  wide  range  of  frequencies.  It  is  this  characteristic  which 
makes  it  available  for  wireless  transmission  purposes. 
Feed  it  alternating  current,  and  it  delivers  direct  current. 
This  characteristic,  just  the  reverse  from  the  preceding 
one,  makes  it  available  as  a  rectifier  for  charging  storage 
batteries,  and,  some  day  in  the  near  future,  as  a  substitute 
'for  the  elaborate  and  costly  rotary  converter  units  now 
necessary  in  electrical  transmission  work,  for  converting 
alternating  current  used  in  high-voltage  transmission,  back 
into  direct  current  of  suitable  voltage  for  commercial  use. 
Feed  it  high-frequency  alternating  current,  such  as  radio 
waves,  and  it  converts  them  into  audible  pulsating  currents 
which  affect  telephone  receivers  and  thus  are  converted 
into  audible  sounds.    That  is  how  it  is  used  as  a  detector. 


RADIO  FOR  EVERYBODY  49 

Feed  it  ever  so  slight  a  fluctuating  current,  and  it  will  con- 
trol or  modulate  or  modify  a  far  more  powerful  current; 
thus  we  have  the  weak  current  moulding  a  powerful  cur- 
rent, and  it  is  this  feature  which  gives  us  the  amplifier. 
It  is  this  characteristic,  too,  that  makes  the  vacuum  tuhe 
the  finest  telephonic  relay  ever  devised.  It  is  used  in  long- 
distance telephone  communication,  so  that  the  voice  cur- 
rents, when  greatly  attenuated  after  traveling  over  hun- 
dreds of  miles  of  wire,  are  Ijrought  to  the  grid  memher 


The  farmer,   using  an  inexpensive  radio   receiving   set,  can  now 

keep    in    touch    with    the    outside    Avorld.      He    hears    the    latest 

musical  "hits,"  and  he  receives  weather  forecasts,  crop  reports, 

and  other  information  of  real   A^alue. 

of  the  vacuum  tube,  and  there  serve  to  control  a  fresh 
and  far  more  powerful  current  which  starts  ofif  on  the 
next  lap  of  the  journey,  only  to  reach  another  vacuum 
tube  when  it  in  turn  has  become  weak  as  a  result  of  a  long 
stretch.  Again,  the  vacuum  tube,  because  of  its  modu- 
lating characteristic,  is  the  link  between  the  carbon  micro- 
phone or  telephone  transmitter  of  the  ordinary  kind,  and 
the  powerful  currents  of  the  radio  telephone  transmitter. 
At  a  stroke  it  eliminates  all  the  troubles  that  seemed  im- 


50  RADIO  FOR  EVERYBODY 

possible  of  solution  back  in  the  early  days  of  the  wireless 
telephone. 

It  was  in  1915  that  definite  progress  was  first  recorded 
in  the  history  of  the  wireless  telephone,  for  it  was  during 
the  latter  part  of  that  year  that  the  engineers  of  the  Amer- 
ican Telephone  and  Telegraph  Company  succeeded  in 
telephoning  by  wireless  between  Arlington,  Va.,  and  the 
Eiffd  Tower,  in  Paris,  or  over  a  distance  of  three  thou- 
sand miles.  Over  three  hundred  vacuum  tubes  were  em- 
ployed to  generate  and  modulate  the  high  frequency  cur- 
rent employed  to  span  the  Atlantic  expanse.  During  the 
same  tests  the  voice  was  carried  through  space  all  the  way 
to  Pearl  Harbor,  in  the  Hawaiian  Islands,  or  a  distance 
of  almost  five  thousand  miles. 

Do  not  forget  that  the  stock  promoters,  back  in  the 
days  when  wireless  telephony  seemed  so  impossible  to 
the  really  wise  men,  were  telling  us  that  the  wireless  tele- 
phone would  be  the  great  rival  of  the  wire  telephone. 
The  wire  telephone  would  certainly  be  put  out  of  business 
in  due  course.  Yet  it  was  only  when  the  engineers  of  the 
wire  telephone  came  to  take  an  interest  in  wireless  tele- 
phony that  this  art  made  real  progress.  What  is  more, 
they  developed  wireless  telephony  to  something  practical; 
and  the  wireless  telephone,  in  turn,  gave  wire  telephony 
the  vacuum  tube  and  other  valuable  devices  which  made 
long-distance  telephony  practical.  So  instead  of  proving 
rivals,  these  two  great  means  of  communication  have  come 
to  be  partners,  and  always  will  remain  partners. 

The  Radio  Link  in   Our  Telephone  System 

Came  the  war,  with  still  greater  progress.  Radio  tele- 
phony on  a  small  scale  had  to  be  perfected,  because  instant 
communication  had  to  be  made  available  between  airplane 
units  and  the  ground  posts.  When  the  United  States 
entered  the  war,  the  best  radio  talent  was  put  to  work  on 
this  problem,  with  the  result  that  the  radio  telephone  in 
small  units  as  well  as  large  units,  became  a  reality.  Today 
it  is  possible  to  obtain  a  radio  telephone  of  5-watt  rating 
capable  of  transmitting  over  a  distance  of  five  to  fifteen 


g.?-? 

B       ? 

""t^ 

SO  3 

^^.^ 

«:§ 

srs-* 

as  *  p 

frSo 

fc!* 

^r 

Ji-a  H 

a  »  S 

^^a 

%*^  o 

»  ?:  S 

IP 

Hi 

S.'S 

2lE 
S3? 

if 

o,^ 


RADIO  FOR  EVERYBODY 


WLEKLY  PROGRAM 
RADIO-PHONE  SERVICE 

WESTINGHOUSE  ELECTRIC  &  Mf  g  Co. 
STATION  W  J  Z.  NEWARK.  N.  J. 

I    MON.,  DEC.  12th,  TO  SUN.,  DEC.   18th,  1921.    I 

This  program  can  be  heard  by  any  one  with 
suitable  radio  receiving  apparatus  within  a  radius 
of  100  miles  of  Newark. 

The  service  is  absolutely  free. 

Tune  Instruments  for  360-meter  waves. 

REGULAR  CONCERT 
DAILY,  8:20  to  9:25  P.  M. 
MONDAY  -  -  -  Mme.    May  Peterson,  Prima 
Donna  Soprano,  Opera  Comique,  Paris 
TUESDAY  - .-  -  Os-Ke-Non-Ton,    Indian   Bar- 
itone; Messrs.  Bertram  Haigh  and  Ralph  Brown, 
French  horns;  Miss  Anita  Wolf,  Pianist 
WEDNESDAY -Mme,  Gretchen  Hood,   Prima 
Donna  Soprano,  Theatre  de  la  Monnai,  Brussels 
THURSDAY  -  -  Miss  Helen  Davis,  Soprano; 
M.  Cliff  Young,  Pianist 
FRIDAY  -  -  -  Westminister  Orchestra 
SATURDAY  -  Dartce  music 
SUNDAY  -  -  Miss  Ethel  Mackey,  Soprano  and 
Miss  Mary  Emerson,  Pianist.  Sacred  Music 

OTHER  FEATURES 

General  News  -  -  Newark   Sunday   Call  News 

Service,  daily,  7:55  P.  M. 
Children's  Hour  -  -  "Man-in-the-Moon"  stories, 
by  Miss  Josephine  Lawrence 
©  Newark  Sunday  Call 
'Tuesday  and  Friday,  7:00  P.  M. 
Hourly  News  Service  -  -  Newark  Sunday  Call; 
weekdays,  every  hour 
from  11.00  A.  M.  to 
7:00  P.M.  on  the  hour 
Radio  Amateurs'  Night  -  -  Thursday  7  P.  M. 

J.  B.  WALKER  editor  Scientific  American 
Weather  Forecast  (Official  Gov't)  -  -  Daily, 

11:00  A.  M.,  5:00  and  10:03  P.  M. 
Marine  News  -  -  Marine    Engineering    Service, 
weekdays   (except   Saturdays),  2:05  P.  M. 
Official  Arlington  Time  -  -  Daily,,  9:55  P.  M. 


(Program  subject  to  change) 


One  of  the  first  programs  of  the  radio- 
phone   broadcasting:    service.       Compare 
this    program    with    one    of   the    present 
programs  reproduced  on  facing  page. 


miles,  as  well  as  a 
5 00- watt  transmitter 
capable  of  spanning 
500  miles  or  more. 
The  war  made  radio 
telephony  what  it  is : 
it  was  not  an  ill  wind, 
for  it  blew  some  good. 
Today,  the  radio 
telephone  is  part  and 
parcel  of  our  wire 
telephone  system,  and 
it  is  fast  becoming  as 
practical  in  its  true 
field  as  the  latter.  In- 
deed, were  it  not  for 
the  high  cost  of  this 
form  of  communica- 
tion, it  would  be  quite 
within  the  scope  of 
present  achievement 
for  any  telephone  sub- 
scriber to  call  up  a 
relative  or  friend  on 
an  ocean  liner  several 
hundred  miles  out  at 
sea,  the  voice  being 
carried  over  the  usual 
telephone  line  to  the 
central  ofifice,  through 
trunk  lines  to  the  dis- 
tant radio  transmitter, 
and  thence  transmitted 
through  the  air  to  the 
steamer.  Two-way 
conversation  could  be 
effected,  as  with  our 
usual  telephone  sys- 
tem.    The  radio  link, 


RADIO  TELEPHONE 
BROADCASTING  PROGRAM 

AVa'  York  Cllu  DIslrirt 


SUN., 


B.  12th,TOSUN.,FEB.19th, 


Sunday 

3  P.  M.— Rndio-Chapel  sen-ices,  "The  Spirit  of 
Lincoln  in  a  R.idio-Unified  World",  by  Rev. 
Ec'par  Swan  Wicrs.  D.D.,  assisted  by  the  quar- 
tette—Mrs. Wm.  M.  Rockwell,  Mrs.  M.  S. 
Powell,  Fred  P.  Taylor  and  George  Roubaud; 
F.  F.  Kuxham,  orpanist — from  Uie  Unitarian 
Church,  Mcntclair,  N.  J. 

4  P.  M. — "Abraham  Lincoln",  an  address  by 
Rev.  Robert  Scott  Inglis,  of  Newark,  \.  J. 

4.S0  P.  M.— 'My  Country  'Tis  of  Thee".  "Star 
Spanded  B.-^nner";  also  several  popular  selections, 
including  -Ty  Tee",  "All  That  I  Need  Is  You"; 
ployed  by  Paul  'U'hitehian's  Orchestra,  from  the 
Palais  RoyrI,  New  York.  Arranged  through  the 
courtesy  of  Leo  Feist,  Inc. 

7.00  P.  M.— Sacred  Music  played  by  the  Aeolian 
Orchestrelle. 

8.00  P.  ^L— "Listen  to  Me",  "Sweet  Lady", 
"Hawaiian  Blues",  and  several  other  selections 
from  Carleton's  Tangerine,  by  members  of  the 
Tangerine  Company,  accompanied  by  the  Casino 
Theatre  Orchestra.  Arranged  through  the  cour- 
tesj'  of  Leo  Feist,  Inc. 

Monday 
2.S0  P.  M.— Ray- Miller's  Record  Orchestra,  assis- 
ted by  Cliff  "Ukelele  Ike"  Edwards. 
8.15  P.  ^L— Miss  Ethel  Grow,  contralto,  who  ap- 
peared in  English  Opera  and  Concert,  and  in 
Oratorio  in  England,  under  the  direction  of  Sir 
Henry  Wood. 

8.-15  P.  M.— Gustav  O.  Homberger,  cellist  of  the 
Kaltenborn  String  Quartette,  who  appeared  in 
concert  with  the  leading  orchestras  of  Europe 
as  solo  cellist  under  Von  Bulow,  Rubinstein, 
Weingartner  and  Richard  Strauss.  Mr.  Horn- 
berger  will  play  a  programme  of  selections  by 
Goltermann,  Chcpin,  and  Moskowski. 

Tuesday 
7  P.M. — "Man-in-the-Moon"  stories  for  children. 
7.45  P.  M. — "Tuberculosis,  Influenza  and  Com- 
mon Colds",  a  preventive  lecture  by  Dr.  Charles 
J.  Hatfield,  Managing  Director  of  the  National 
Tuberculosis  .Association. 

8.00  P  M. — .\n  address  on  radio  by  Paul  F. 
Godley. 

8.20  P.  M. — A  second  recital  to  the  radio-phone 
audierce  by  Mme.  Gretchen  Hood,  Prima  Donna 
Soprano,  Theatre  De  La  Monnair,  Brussels;  also 
of  the  San  Carlo  Opera  Company,  and  prominent 
concert  singer.  Her  program  includes  "Seger- 
bella"  from  Carmen,  Bizet,  and  a  group  of  bal- 
lads. Courtfsy  of  Aeolian  Company. 
8.45  P.  M. — '.'Che  Gelida  Manina"  from  the  Opera 
Boheme,  Buccini,  etc.,  ty  Charles  Harrison,  Tenor 
Soloist,  Fifth  Avenue  Brick  Presbj'terian  Church, 
for  four  years;  studied  with  Frederick  Bristol. 
9.20  P.  M. — Songs  and  readings  by  Mr.  and  Mrs. 
E.  E.  HoUe,  of  Newark,  N.  J. 

Wednesday 
8.15  P.  M. — ^Descriptive  recital  with  music,  of 
Verdi's  opera,  "D  Trovatore." 

Thursday 
7.45  P.  M  — "Modern  Health  Problems",  an  ad- 
dress bv  Dr.   Royal  S.    Copeland,   Commission- 
er  of  'Health.  New  York  Citv. 
8.00  P.  M.— "TMiat  is  a  Rotary  Club  and  ^"hat 
Are  its  Relations  to  the  Public"  by  Allan  Smith, 


THUR.SDAY  (conlimied) 
Ex-President  of  the  Newark  Rotary  Club.    Also 
a  rotary  song  by  Andrew  Krenrich. 
8.20  P.  M.—  Classical  music. 

O.iO  P.  M. — A  program  of  songs  by  Janet  Bush-. 
Hecht,  contralto  soloist,  First  Congregational 
Church,  Montclair,  N.  J.,  and  a  prize  winner  in  a 
Newark  Music  Festival  Contest.  The  program 
includes  "In  Flanders  Fields",  "Would  You," 
"Bubbles",  and  "Joyous  Youth",  composition, 
of  Mabelanna  Corby,  who  will  be  the  accompanist 
for  these  and  other  selections.  Courtesy,  Aeolian 
Company. 

Friday 
7.00 — "Man-in-the-Moon"  stories  for  children. 
8.15  P.  M.— "Party  Night,"  when  several  well- 
known  artists  of  vaudeville  and  the  musical  com- 
edy stage  will  entertain  with  songs  and  mono- 
logues. 

Saturday 
7.00  P.  M.— Irv  Pages  Cornell  Orchestra,  Cornell 
University,  composed  of  the  following:  Irv  Page, 
banjo;  Geo.  Cox,  banjo;  Lyman  Breese,  banjo; 
Sam  Bird,  traps  and  drums;  Jack  Wallace,  saxa- 
phone;  and  Paul  Miller,  cornet,  banjo  and  violin. 
7.45  P.  M.— "Fa.shion  Talks  to  Women",  Mar- 
jorie  Wells,  N.  Y'.  World. 

8.00  P.  M.—  The  "Daily  Dozen"  exercises 
address,  by  Walter  Camp,  foremost  authority  in, 
American  athletics. 

8.20  P.  M.— Dance  Music  by  the  Femwood  Dance 
Orchestra  of  Newark,  N.  J. 

9.20  P.  M. — Popular  and  character  songs  by 
Ailcen  Stanley,  soprano,  well-known  in  vaudeville 
circles. 

9.45  P.  M.— "Hello  Prosperity",  "Don't  Leave 

Me  Mammy",   etc.,   by  Max  Hitrig,  dramatic 

tenor,  known  from  Coast  to  Coast. 

Duo  Art  Piano  Recital. 

Sunday 

3  P.  M.— Radio-Chapel  Services,  Rev.  Clarence 
H.  Wilson,  D.D.,  Glen  Ridge  Congregational 
Church. 

4  P.  M. — "Boys  of  the  World",  an  address  by 
C.  R.  Scott,  State  Secretary  of  Boys'  Work, 
Y.  M.  C.  A.,  Newark,  N.  J.  Music  by  quartette 
including  Miss  May  Korb,  soprano  soloist,  South 
Park  Presbyterian  Church;  jVIiss  Marian  Adams, 
contralto  soloist.  Church  of  the  Redeemer;  Bruce 
Campbell,  tenor,  and  Louis  Burke,  baritone,  Clin- 
ton Avenue  Reform  Church. 

6  P.  M. — Program  of  classical,  music  by  Mrs. 
Robt.  Baldwin,  ^■ioli^ist  and  Mrs.  Ernest  H. 
Harder,  pianist. 

7.45  P.  M. — Sacred  Music  recital  by  the  Aeolian 
Orchestrelle. 

8.00  P.  j\I. — ^Ed  Wynn  and  the  entire  company 
of  "The  Perfect  Fool",  now  playing  at  Geo.  M. 
Cohan's  Theatre,  New  York.  For  the  first  time 
in  the  history  of  radio  an  attempt  will  be  made  to 
broadcast  an  entire  theatrical  performance.  Ar- 
ranged by  the  N.  Y'.  Globe. 

OTHER  FEATURES 
Musical  Program  wcelidays,  every  hour  from  11  a.m, 

to  6  p.  m.  on  the  hour. 

"FASHIO.V  TALKS  TO  WOMEN",  MarjorieWetlB.  N.    T.    World 


Ensineering 

BABSON'S  Statistical  Service.  Monday.  8  P.  M. 

OFFTCAL  ARLINGTON  TrME  9.52  P.  M. 

AGRICULTURAL  REPORTS.  Official,  daily  12.00  M..  and  6.00P.M 

"MAN-IN-THE-MOON"      stories    by     Miss   Josephine    Lawrence 

(©NewarkSundayCall). 

(■Program  will  be  announced  daily   by  radio  pham  7.45  P.  M.> 


A    typical    printed    program    of    a    single    radio-phone    broadcasting 

station.       Such    programs    are    mailed    out    to    interested    parties    in 

order    that    one    may    know    what    to    look    for    every    evening    of    the 

forthcoming    week. 


54  RADIO  FOR  EVERYBODY 

as  the  radio  telephone  service  is  called  when  used  in  this 
manner,  is  destined  to  become  commonplace  within  the 
next  few  years. 

Now  the  foregoing  is  no  mere  flight  of  fancy.  It  is  a 
matter  of  record  that  the  American  Telephone  and  Tele- 
graph Company  recently  conducted  a  series  of  experiments 
with  radio  links  and  the  trans-continental  telephone  line. 
Telephonic  communication  was  established  between  the 
steamship  ''Gloucester,"  cruising  off  Deal  Beach,  N.  J., 
and  Santa  Catalina  Island,  situated  some  thirty  miles  off 
the  California  mainland  in  the  vicinity  of  Long  Beach. 
The  telephonic  communication,  in  this  case,  passed  from 
the  "Gloucester"  to  Deal  Beach,  N.  J. ;  from  Deal  Beach 
to  New  York  via  telephone  line;  from  New  York  to  San 
Francisco  via  trans-continental  telephone  line ;  from  San 
Francisco  to  Los  xA.ngeles  via  telephone  line ;  from  Los 
Angeles  to  Long  Beach  via  telephone  line ;  and  from  Long 
Beach  by  radio  to  Pebbly  Beach,  on  Santa  Catalina  Island, 
and  from  Pebbly  Beach  to  the  Avalon  exchange.  From 
ocean  to  ocean  via  radio,  telephone  line,  radio  again  and 
telephone  line,  through  all  the  various  circuits  without 
appreciable  distortion ! 

The  first  commercial  radio  and  connecting  land  toll  line 
is  the  Santa  Catalina  Island  and  California  radio  link, 
which  was  set  in  operation  the  latter  part  of  1920.  Radio 
telephone  service  between  Santa  Catalina  and  the  main- 
land to  connect  up  with  the  Bell  system  exchanges  was 
installed  at  the  request  of  the  local  telephone  company. 
Catalina  is  one  of  the  great  tourist  resorts  in  California. 
It  attracts  thousands  of  visitors  daily  throughout  the 
year,  who,  heretofore,  when  they  left  the  California  main- 
land, remained  completely  isolated  from  the  rest  of  the 
world  until  they  returned  to  the  mainland,  except  for  the 
much  overloaded  naval  radio  telegraph  station  on  the 
island. 

That  this  radio  link,  which  bridges  the  31^-mile  gap 
between  the  island  and  the  mainland,  is  not  in  the  experi- 
mental stage  may  be  gathered  from  the  fact  that  it  handles 
hundreds  of  messages  each  day.     The  large  amount  of 


56  RADIO  FOR  EVERYBODY 

commercial  traffic  with  scarcely  any  interruption  which 
the  Avalon-Los  Angeles  toll  circuit  has  carried  since  its 
inauguration  is  ample  proof  of  the  practicability  of  toll 
lines  containing  radio  links,  where,  due  to  physical  condi- 
tions, direct-wire  connections  are  impracticable. 

It  is  virtually  impossible  to  delve  deeply  into  the  intrica- 
cies of  the  Avalon-Los  Angeles  radio  link  and  wire  cir- 
cuit, since  it  involves  the  moat  elaborate  telephone  and 
radio  engineering  practice  extant.  Suffice  it  to  state  that 
the  circuit  consists  of  a  little  more  than  one  mile  of  wire 
line  from  the  Avalon  central  office  to  Pebbly  Beach,  a 
31^-mile  radio  link  to  Long  Beach,  and  25  miles  addi- 
tional wire  circuit  to  Los  Angeles.  This  combination 
wire  and  radio  circuit  is  operated  as  a  unit,  providing 
through  telephone  and  signalling  from  Avalon  to  Los 
Angeles.  At  Avalon  the  circuit  may  be  connected  to  any 
local  subscriber's  line,  and  at  Los  Angeles  to  any  local 
subscriber's  line,  through  local  exchanges,  or  with  other 
long-distance  lines  reaching  practically  any  subscriber  in 
the  Bell  system. 

The  radio  link  is  a  duplex  system:  one  message  may 
be  sent  in  each  direction  simultaneously.  For  transmit- 
ting, a  fair-sized  aerial  is  employed,  while  for  receiving 
a  loop  antenna  is  used  at  each  end.  These  loops  are  of 
the  solenoidal  or  helical  type,  six  feet  square,  and  consist 
of  only  four  or  five  turns  each.  To  make  the  duplex 
operation  a  success,  it  goes  almost  without  saying  that 
exceptional  measures  had  to  be  taken,  otherwise  the  trans- 
mitter at  one  end  would  drown  out  the  incoming  signals 
on  the  loop  antenna  but  a  short  distance  away.  The  elimi- 
nation of  such  interference  was  attained  by  the  use  of 
different  carrier  frequencies  for  transmission  in  the  two 
directions. 

Great  things  can  be  expected  of  the  radio  link.  Whereas 
it  would  otherwise  be  necessary  for  a  person,  desiring 
to  telephone  by  wireless,  to  have  a  radio  telephone  trans- 
mitter of  his  own  or  to  visit  a  radio  telephone  station,  it 
now  becomes  possible  to  employ  a  distant  radio  telephone 
transmitter  through  any  Bell  system  telephone.    It  is  only 


58  RADIO  FOR  EVERYBODY 

a  matter  of  time  when  we  shall  talk  over  our  telephone 
lines  to  our  friends  at  sea,  thanks  to  the  radio  link, 
although  this  service  will  always  of  necessity  be  expensive. 

How  Radio-Phone  Broadcasting  Came  About 

But  the  average  reader  of  this  book  will  no  doubt  be 
more  interested  in  the  radio-phone  broadcasting  develop- 
ment, which  is  a  later-day  phase.  Before  this  broadcast- 
ing service  became  a  regular  thing,  there  were  spasmodic 
efforts  to  send  out  musical  programs,  made  by  several 
radio  companies,  but  these  were  intended  rather  as  tests 
than  as  entertainment  for  tens  of  thousands  of  listeners. 
The  present  form  of  radio-phone  broadcasting  dates  back 
to  the  latter  part  of  1920,  when  the  Westinghouse  Elec- 
tric and  Manufacturing  Company  inaugurated  the  firsr 
radio-phone  concert  through  its  Pittsburgh  station.  Only 
a  small  number  of  persons  heard  the  musical  numbers 
sent  out  by  KDKA,  the  Westinghouse  station  in  Pitts- 
burgh. The  phonograph  was  the  only  source  of  music, 
and  the  operator's  announcements  sufficed  for  lectures 
and  talks.  The  novelty  of  the  feat  was  sufficient,  of 
course,  for  the  public  had  not  yet  been  pampered,  so  to 
say.  Problems  arose  over  the  manner  and  method  of 
broadcasting,  which  had  to  be  solved  by  experiment. 
There  were  many  times  during  the  first  few  weeks  of 
broadcasting  when  the  concerts  were  anything  but  pleasant 
to  the  ear.  Then,  as  time  passed  on  and  through  experi- 
ence the  operators  found  out  for  themselves  the  kind  of 
phonograph  records  which  transmitted  clearly  and  those 
which  did  not,  what  to  avoid  in  the  way  of  speech,  what 
pleased  the  public  and  what  raised  its  ire,  and  the  various 
other  little  details  which  made  or  marred  a  radio  perform- 
ance, the  concerts  began  to  pick  up  not  a  little. 

During  this  experimental  stage  letters  began  to  trickle 
in  from  various  parts  of  the  country,  telling  of  the  re- 
ception of  music  and  talks  from  KDKA.  At  first,  returns 
were  small,  and  mostly  replies  from  established  stations, 
which  are  always  on  the  lookout  for  new  developments, 
in  radio.     These  stations,  by  the  way,  lose  no  time  in 


RADIO  FOR  EVERYBODY  59 

corresponding  with  other  stations  they  hear.  After  a 
time  letters  began  to  come  from  persons  who  had  only 
recently  purchased  receiving  sets,  perhaps  after  hearing 
the  concerts  at  one  of  the  amateur  stations.  These  lay- 
men increased  in  a  steady  stream  and  their  number  even 
at  this  writing  increases  steadily  by  leaps  and  bounds, 
Radio  manufacturers  are  months  behind  in  their  produc- 
tion. 

Practically  all  the  broadcasting  by  KDKA  was  pioneer- 
ing work.  For  instance,  take  the  case  of  the  radio  church 
services.  When  the  station  was  started,  there  was  no 
program  developed  for  Sunday  evening.  It  was  sug- 
gested that  church  services  be  tried.  There  was  no  prece- 
dent for  this  method  of  radio  transmitting  and  conse- 
quently it  was  not  known  whether  church  services  would 
broadcast  well  or,  indeed,  if  the  churches  would  consent 
to  this  method  of  handling  their  services.  After  some 
persuasion,  however,  permission  was  received  from  Cal- 
vary Episcopal  Church  of  Pittsburgh,  to  broadcast  its 
services.  A  district  telephone  line  was  installed  between 
the  church  and  the  radio  station  for  this  purpose. 

Four  microphones  were  installed  in  the  church,  to 
catch  the  voice  of  Edwin  J.  Van  Etten,  rector  of  the 
church,  the  choir,  the  chimes,  and  the  organ,  and  the  en- 
tire services  were  first  sent  out  January  2nd,  1921.  No 
one  thing  ever  broadcasted  by  the  radio  station  has  been 
so  popularly  received.  Letters  poured  in  by  the  score  to 
the  Radio  Division,  telling  of  the  pleasure  and  benefit  of 
this  new  department  in  radio.  Newspapers  all  over  the 
country  carried  editorial  announcements  of  the  fact  that 
church  sermons  were  being  broadcasted  from  Pittsburgh 
through  the  medium  of  the  radio-phone.  This  was  the 
first  eflFort  of  its  kind ;  and  it  made  the  radio-phone  safe 
for  the  future. 

From  Canned  Music  to  the  Real  Thing 

After  a  time,  when  the  church  services  were  well  known 
to  all  radio  enthusiasts  because  of  the  clearness  of  trans- 
mission,  the   Westinghouse  Company   was   requested  by 


60  RADIO  FOR  EVERYBODY 

members  of  the  Herron  Avenue  Presbyterian  Church  to 
install  a  receiving  set  and  loud  speaker  to  take  the  place 
of  a  long  absent  pastor.  This  was  done,  and  the  church 
assembled  for  an  Episcopal  service.  But  it  listened  to  a 
sermon  preached  about  fourteen  miles  away.  This  serv- 
ice, it  goes  without  saying,  was  also  a  record,  a  milestone, 
if  you  please,  since  it  was  the  first  time  two  congrega- 
tions in  separate  churches  had  ever  worshipped  to  one 
service,  when  a  distance  of  miles  separated  them.  It  was 
also  the  first  time  that  u  metallic  horn  ever  took  the 
place  of  a  flesh-and-blood  minister.  Again,  this  feat,  al- 
most in  the  miracle  class  were  it  not  for  the  fact  that  we 
have  come  to  expect  such  marvelous  things  from  modern 
science,  attracted  the  attention  of  the  press,  with  the  result 
that  more  people  than  ever  began  to  take  an  active  inter- 
est in  the  radio  telephone. 

In  the  meantime  phonograph  records  comprised  most 
of  the  evening  musical  programs.  It  was  decided  to  do 
away  as  much  as  possible  with  the  ''canned"  music  and 
substitute  real  singers  and  musicians.  Talent  was  not 
hard  to  obtain  for  this  work,  in  most  cases  volunteering 
its  services.  Human  voices  began  to  come  over  the  radio 
telephone  instead  of  records,  and  were  an  agreeable  change. 
Again  an  improvement  was  made  in  radio  broadcasting — 
another  milestone.  Not  satisfied  with  having  merely  local 
talent,  the  Radio  Division  of  the  Westing^house  orgfani- 
zation  entered  into  an  agreement  with  the  managers  of  the 
local  operatic  concerts,  with  the  result  that  when  stars  of 
the  first  magnitude  came  to  Pittsburgh,  their  efforts,  vocal 
and  instrumental,  were  and  are  being  broadcasted  over 
hundreds  of  miles. 

Not  only  in  opera,  but  in  the  world  of  sport,  the 
radio-phone  service  has  been  introduced.  Casting  about 
for  features  that  would  enliven  the  evening  programs,  it 
was  decided  to  'broadcast,  as  an  experiment,  blow-by-blow^ 
returns  of  a  boxing  match  held  in  Pittsburgh.  A  private 
wire  was  installed  from  a  boxing  club  to  the  radio  sta- 
tion, and  a  man  prominent  in  sporting  circles  engaged  to 
render  a  round-by-round  version  of  the  progress   of  the 


RADIO  FOR  EVERYBODY  61 

fight.  So  KDKA  was  the  first  broadcasting  station  ever 
to  send  out  fight  returns.  Afterwards,  the  Dempsey- 
Carpentier  bout  in  Jersey  City,  N.  J.,  was  broadcasted  by 
a  Radio  Corporation  station  round  by  round. 

But  operatic  engagements  and  boxing  bouts  do  not 
cover  the  entire  gamut  of  pubhc  interest.  So  to  the 
existing  features  there  were  added  the  news  of  the  day, 
weather  forecasts,  agricultural  reports,  and  other  items  of 
general  interest,  not  to  forget  the  occasional  addresses 
by  prominent  men. 

In  order  to  perfect  the  transmission  of  music  and 
speeches  by  radio,  the  Westinghouse  engineers  have  made 
considerable  researches  of  the  different  frequencies  of 
both.  A  studio  has  been  built  especially  for  the  artists  who 
sing,  so  that  the  radio-phone  reproduction  will  be  accur- 
ate. The  studio  in  East  Pittsburgh  consists  of  a  room 
:^0  by  30  feet,  completely  lined  with  burlap  and  devoid  of 
windows,  so  that  there  w^ill  be  no  reflection  of  sounds. 
A  report  is  made  of  every  song,  where  the  singer  stands, 
how  far  away  from  the  transmitters,  and  other  incidental 
details.  This  report  is  checked  up  later  with  a  receiving 
station  and  from  this  data  considerable  information  has 
been  obtained  regarding  the  transmission  of  various  kinds 
of  music.  This  is  only  by  way  of  showing  ho'w  the  new 
art  has  had  to  be  developed,  step  by  step. 

Extending  the  Broadcasting  Area 

So  successful  did  the  East  Pittsburgh  radio-phone  sta- 
tion prove  and  so  great  was  the  interest  shown  by  the 
public  and  reflected  by  the  unprecedented  and  even  un- 
dreamed of  demands  for  radio  receiving  equipment  that 
the  Westinghouse  organization  set  to  work  opening  up 
other  broadcasting  stations.  At  Newark,  N.  J.,  on  the 
roof  of  the  Company's  plant,  there  was  installed  a  power- 
ful broadcasting  transmitter  known  as  WJZ.  Down  on 
the  first  floor  of  the  building  there  is  an  attractive  studio, 
equipped  with  various  musical  instruments  and  hung 
with  curtains  to  make  it  sound-proof.  In  this  studio  ar- 
tists have  been  singing  and  playing,  while  speakers  have 


p 

aa'3 


•IH     e 


S  to. 

5  c 

-Ox 

§1 

11 

^  o 
■*^'^ 
fceg 

l» 


O  ^ 

Jo 


Ms 

^  a 
^  a 

u  u 

ft  . 


=3W 


RADIO  FOR  EVERYBODY  63 

delivered  their  messages,  for  the  benefit  of  the  greatest 
audience  ever  gathered  at  one  time.  It  is  estimated  that 
over  300,000  persons  hear  the  concerts  and  talks  broad- 
casted by  the  Newark  radio-phone  station,  and  that  the 
effective  area  covered  by  this  service  takes  in  one-tenth 
of  our  total  population.  The  service  of  this  station  can 
be  heard  by  anyone  within  a  radius  of  100  miles  of 
Newark,  though  as  a  matter  of  fact  reports  of  the  re- 
ception of  the  musical  numbers  and  talks  have  come  from 
Canada,  Wisconsin,  Florida,  Cuba,  and  600  miles  out  at 
sea. 

Then  there  is  the  Springfield  station,  known  as  WBZ, 
which  supplies  New  England  with  the  Westinghouse 
radio-phone  service.  Another  station  has  been  established 
in  Chicago,  known  as  KWY,  and  is  intended  for  the 
Middle  West  and  the  Western  States. 

The  W^estinghouse  programs  are  of  a  high  order  and 
provide  a  wide  variety  of  entertainment.  Thus  the  New- 
ark station,  WJZ,  every  evening  from  8  :20  to  9  :15  broad- 
casts a  concert  with  well-known  operatic  or  concert  stars 
frequently  singing  or  playing  in  -person.  At  8  :00  a  digest 
of  the  day's  news  is  sent  out.  An  especially  popular 
feature  is  the  "Man-in-the-Moon"  fairy  tales  for  children. 
As  this  is  written  these  bedtime  stories  are  sent  out  on 
Tuesdays  and  Fridays  at  7  :00  p.  m.  The  stories  delight 
the  youngsters  all  over  the  reception  area.  At  many 
of  these  parties  the  children  are  ushered  into  a  darkened 
room  just  before  7  :00  p.  m.,  and  each  is  handed  a  tele- 
phone receiver  connected  with  the  receiving  set.  An 
illuminated  moon  lends  atmosphere  to  the  occasion.  Sud- 
denly, out  of  the  silence,  comes  a  voice — "Hello  children, 
are  you  listening?  This  is  the  Man-in-the-Moon"  talking. 
What  do  you  suppose  I  saw  today?" — and  a  wonder-story 
follows,  interspersed  wnth  musical  selections. 

In  addition,  news  bulletins  are  given  out  during  the 
day,  every  hour  on  the  hour;  the  official  Government 
weather  forecast  is  sent  out  three  times  a  day ;  and  the 
official  Arlington  time  signals  are  made  available  for 
amateur  receivers  at  9  :55  p.  m.,  with  the  final  dash  at 


64  RADIO  FOR  EVERYBODY 

10 :00  sharp.  Other  features,  such  as  election  returns, 
bulletins  of  championship  baseball  and  football  games  via 
direct  telephone  line  from  the  fields,  lectures  by  famous 
scientists,  and  so  on,  are  given  from  time  to  time.  These 
details  are  announced  in  advance  over  the  radio-phone  and 
are  given  in  -weekly  programs  issued  by  the  Company. 
Indeed,  it  is  the  certainty  of  the  present  radio-phone  serv- 
ice that  makes  it  so  interesting.  One  can  look  forward  to 
some  definite  evening  because  the  musical  program  of 
that  evening  happens  to  be  of  most  interest.  It  is  very 
much  like  going  to  a  concert  or  vaudeville ;  for,  while 
the  actual  performance  cannot  be  seen,  although  it  is 
clearly  heard,  this  obstacle  is  perhaps  more  than  counter- 
balanced in  many  instances  by  the  fact  that  the  audible 
side  of  the  performance  is  brought  right  into  the  home. 

The  Springfield  station,  in  addition  to  many  of  the 
foregoing-mentioned  features,  sends  out  a  periodical  talk 
to  farmers  about  market  and  stock  conditions.  The  com- 
plete ^transmission  of  grand  opera  from  the  Chicago  Opera 
Company  productions  has  been  the  feature  of  the  recently 
established  station  on  the  Commonwealth  Edison  Build- 
ing in  Chicago.  It  is  possible  that  the  radio-phone  in 
time  wiH  ht  as  popular  in  the  home  as  the  phonograph 
is  today.  But  its  destiny  rests  entirely  in  the  hands  of 
those  who  supply  the  broadcasting  service,  to  be  sure. 

Aside  from  the  Westinghouse  organization,  there  are 
other  broadcasting  stations.  During  the  pioneer  days  of 
broadcasting  the  Radio  Corporation  of  America's  station 
at  Roselle  Park,  N.  J.,  known  as  WDY,  did  excellent 
work.  At  the  time  of  this  writing  this  station  has  been 
discontinued,  leaving  much  of  the  broadcasting  in  the 
Middle  Atlantic  States  to  WJZ.  The  Roselle  station  was 
known  for  its  operatic  concerts,  which  included  a  lecture 
on  the  opera  of  the  evening,  together  with  the  best  selec- 
tions from  that  opera.  Then  there  were  the  radio  par- 
ties, which  were  made  up  of  songs,  talks,  dialogues,  mono- 
logues and  other  vaudeville  features. 

There  are  various  other  organizations  devoting  a 
goodly  part  of  their  efforts  to  broadcasting  radio-phone 


RADIO  FOR  EVERYBODY  65 

news  and  concerts.  In  fact,  as  things  stand  at  present 
it  is  safe  to  state  here  that  virtually  every  part  of  the 
United  States  is  covered  by  one  or  more  stations.  To 
give  a  list  of  stations  is  virtually  impossible,  for  in  an 
art  that  is  so  new  there  are  bound  to  be  frequent  changes. 
Hence  no  attempt  is  being  made  to  offer  a  list,  because  it 
would  be  hopelessly  obsolete  by  the  time  it  got  into  print. 
The  reader  is  referred  to  the  radio  periodicals  and  to  the 
daily  newspapers  that  have  radio  sections,  for  the  last- 
minute  information  on  radio-phone  stations. 

As  it  is,  the  WJZ  or  Newark  station  of  the  Westing- 
house  organization  is  shortly  going  out  of  existence  as 
this  is  being  written.  Word  has  gone  out  to  the  effect 
that  the  American  Telephone  &  Telegraph  Company, 
which  is  a  factor  in  the  Radio  Corporation  of  America 
combine,  is  about  to  open  a  radio-phone  broadcasting 
station  on  the  roof  of  its  24-story  building  on  Walker 
Street,  New  York  City.  Steel  towers  100  feet  high  will 
support  the  aerial,  and  the  station  will  be  far  more 
powder ful  than  WJZ  which  it  is  replacing. 

With  an  Eye  to  the  Future  ^ 

This  radio  broadcasting  station  will  be  unique  in  many 
respects.  The  distributing  station  is  to  be  equipped  with 
the  latest  developments  of  the  Bell  system,  including  the 
use  of  electrical  filters  and  new  methods  whereby,  as  the 
business  growls,  several  wave  lengths  can  be  sent  out  simul- 
taneously from  the  same  point,  so  that  the  listening 
station  may  receive  at  will  any  one  of  several  services 
sent  out  at  the  same  time. 

The  telephone  organization  will  provide  channels 
through  which  any  one  with  whom  it  makes  a  contract 
can  send  out  his  own  pragrams,  just  as  the  company  leases 
its  long-distance  telephone  wire  facilities  for  the  use  of 
newspapers,  banks,  and  other  concerns.  There  have  been 
many  requests  for  such  a  service,  not  only  from  news- 
papers and  entertainment  agencies,  but  also  from  depart- 
ment stores  and  a  great  variety  of  business  houses,  ac- 
cording to  a  telephone  official. 


(j6  radio  for  everybody 

The  station  when  completed  will  cover  a  territory 
within  a  radius  of  from  100  to  150  miles  of  New  York 
City,  and  imder  particularly  favorable  conditions  may 
be  able  to  operate  over  a  greater  territory.  It  is  estimated 
that  more  than  11,000,000  persons  reside  in  the  territory 
to  be  covered  by  the  new  plant. 

This  is  a  new  undertaking,  true,  and  the  fact  is  fully 
appreciated  by  the  telephone  organization.  If  there  should 
appear  to  be  a  real  field  for  such  service  and  it  can  be 
furnished  sufficiently  free  from  interference  in  the  ether 
from  other  radio  services,  it  will  be  followed  as  cir- 
cumstances warrant  by  similar  stations  erected  at  impor- 
tant centers  throughout  the  United  States  by  the  American 
Telephone  and  Telegraph  Company.  As  these  additional 
stations  are  erected,  they  can  be  connected  by  the  toll  and 
long-distance  wires  of  the  Bell  system  so  that  from  any 
central  point  the  same  news,  music  or  other  program  can 
be  sent  out  simultaneously  through  all  these  stations  by 
wire  and  radio  with  the  greatest  possible  economy  and 
without  interference. 

While  it  is  entirely  possible,  as  has  been  demonstrated, 
to  talk  across  the  continent  or  even  for  much  greater  dis- 
tances over  water  by  radio  when  all  atmospheric  conditions 
are  favorable,  such  long-distance  radio  telephone  trans- 
mission at  present  is  not  dependable  and  is  not  to  be 
compared  from  a  standpoint  of  service  or  economy  with 
the  transmission  which  is  provided  over  wire.  However, 
for  a  broadcasting  service,  which  involves  only  one-way 
transmission,  where  the  same  message  is  given  simultane- 
ously to  a  great  number  of  people  within  reasonable  dis- 
tances of  the  transmitting  station,  radio  telephony  offers 
a  promising  field  for  development. 

Heretofore,  the  broadcasting  services  have  been  sent 
out  at  considerable  expense  by  the  companies  operating 
radio-phone  stations,  without  charge  to  the  sender  or  the 
receiver  of  the  messages  or  music.  However,  it  is  abso- 
lutely obvious  that  the  interest  created  in  radio  has  been 
multiplied  thousands  of  times  by  the  radio-phone  service, 
and  there  has  sprung  up  a  demand  for  radio  receiving 


RADIO  FOR  EVERYBODY  67 

apparatus  that  has  exceeded  the  wildest  expectations. 
Radio  -manufacturers  in  many  instances  are  months  behind 
in  their  dehveries,  and  their  greatest  problem  is  produc- 
tion. This,  mind  you,  at  a  time  when  practically  every 
other  line  of  business  is  searching  every  nook  and  corner 
for  a  buyer ! 

However,  it  must  be  obvious  that  this  gratuitous  service 
cannot  continue  indefinitely.  A  time  must  come  when 
the  radio  market  will  be  pretty  well  saturated,  and  it  will 
no  longer  'be  attractive  for  companies  to  furnish  free 
radio-phone  service.  No  doubt  by  then  the  Government 
will  be  furnishing  all  kinds  of  news,  such  as  agricultural 
reports,  weather  forecasts,  official  time  signals,  commer- 
cial reports,  and  so  on  by  radio-phone,  but  there  will  still 
be  a  demand  for  musical  entertainment. 

So,  the  way  it  seems  now,  the  radio-phone  service  of 
the  future  must  be  a  cross  between  a  special  publicity 
service  and  a  free  program.  There  will  be  free  service, 
the  same  as  now ;  there  will  be  musical  numbers,  news 
of  the  day,  weather  forecasts,  and  so  on;  but  in  addition 
there  must  be  an  occasional  talk  on  the  offerings  of  the 
leading  department  store,  a  subscription-'getting  chat  by 
the  editor  of  a  large  magazine,  a  campaign  speech  by  a 
candidate  for  public  office,  and  so  on.  It  will  be  the 
toll  charged  for  such  broadcasting  service  that  will  pay 
for  the  radio-phone  concerts  and  news.  It  must  come 
to  that,  sooner  or  later. 

Already  department  stores  and  others  have  planned  and 
are  going  ahead  with  radio-phone  transmitters,  with  the 
object  of  sending  out  entertainment,  news,  and  their  own 
particular  brand  of  publicity.  Interesting  as  this  work 
may  be,  there  is  always  a  grave  danger  that  it  may  be 
overdone.  For,  let  it  be  remembered,  there  is  only  a 
limited  amount  of  radio  traffic  that  can  'be  borne  on  the 
ether  highways.  It  wouldn't  take  many  radio-phone  trans- 
mitters in  any  one  locality  to  crowd  each  other  so  hard 
that  a  hopeless  tangle  would  ensue.  That  is  why  the 
thought  of  radio-phone  transmission,  which  is  unfortun- 
ately so  persistent  with  many  amateurs  and  business  or- 


.=  SO 


s  s2 


—     « 

3 1* 

O  fl 

s  a  ^ 
-t-  :«  o 
*    .a 

o  o  aj 

h   IB  J- 


2o« 


*  c  i 
«  e 


<^ 


RADIO  FOR  EVERYBODY  m 

ganizations,  must  be  discouraged,  particularly  in  crowded 
areas.  The  ether  must  be  kept  free  and  clear  for  the 
better  class  of  radio-phone  services.  It  must  and  will  be  a 
survival  of  the  fittest,  for  the  Government  must  step  in 
and  see  that  only  those  with  a  real  service  to  offer  are 
permitted  to  travel  the  ether  highways,  so  long  as  our 
present  knowledge  of  the  art  affords  but  a  Hmited  number 
of  available  wave  lengths  with  which  to  operate. 

And  at  the  Receiving  End 

The  radio-phone  service  of  the  present  or  the  future 
is  available  to  everyone  provided  with  a  suitable  receiv- 
ing set.  All  that  is  necessary  is  some  kind  of  aerial,  which 
for  this  purpose  may  be  a  single  wire,  elevated  20  or  more 
feet  off  the  ground,  and  running  longer  than  100  feet  if 
possible.  About  150  feet  is  the  best  length,  and  there  is 
no  decided  advantage  in  running  a  longer  wire  for  the 
reason  that  the  wave  length  of  the  radio-phone  services 
is  generally  around  360  meters,  and  it  is  best  to  have  the 
natural  wave  length  of  the  aerial  as  near  this  value  as 
possible.  With  a  -much  longer  wire,  it  becomes  necessary 
to  insert  a  condenser  in  series,  and  this  only  reduces  the 
efficiency  of  the  aerial  by  that  much.  Hence  150  feet  of 
■wire  is  recommended.  Aside  from  this  simple  aerial,  a 
ground  connection  is  necessary.  For  this  purpose  a  con- 
nection may  be  made  to  a  steam  radiator  pipe,  water  pipe, 
gas  pipe,  or  to  any  object  which  is  known  to  be  connected 
with  the  ground  in  an  efficient  manner.  In  the  country, 
where  steam  pipes,  gas  pipes  and  water  pipes  are  not 
available,  a  good  ground  may  be  obtained  by  running  a 
wire  to  a  zinc  or  copper  plate,  and  then  burying  the  plate 
some  six  feet  under  the  ground,  in  moist  soil.  Again,  a 
wire  may  be  connected  to  a  pail  which  is  lowered  into 
a  well  or  into  a  brook  or  lake. 

As  will  be  explained  in  detail  further  on,  the  receiving 
set  to  use  depends  entirely  on  the  distance  between  the 
receiving  station  and  the  broadcasting  station.  Thus 
within  a  25-mile  range,  a  simple  receiving  set  will  do. 
Beyond  this  range  and  up  to  50  or  75  miles,  a  better  re- 


•J'O  '   RADIO  FOR  EVERYBODY 

ceiving  set  must  be  used,  and  it  calls  for  a  storage  bat- 
tery or  large  dry  battery  to  operate  the  vacuum  tube 
detector  which  then  replaces  the  crystal  detector  used  for 
shorter  ranges.  For  still  greater  ranges,  a  vacuum  tube 
detector  and  a  vacuum  tube  amplifier  unit  must  be  em- 
ployed, and  the  set  then  begins  to  mount  up  into  con- 
siderable money.  Even  for  short  ranges,  where  a  loud- 
speaking  telephone  is  desired,  an  amplifier  must  be  em- 
ployed, for  it  is  the  amplifier  which  builds  up  the  radio 
waves  so  that  they  can  be  converted  into  loud  sound  waves 
and  heard  throughout  a  larger  room,  thus  doing  away 
with  the  necessity  of  wearing  the  usual  head  'phones. 

There  is  nothing  more  facinating  than  listening  to  the 
radio-phone  concert  and  service.  One  turns  the  tuning 
handle  of  the  receiving  set :  short  and  long  buzzes,  fol- 
lowing each  other  in  a  lazy  sort  of  way,  indicate  some 
amateur  radio  telegraph  transrnitter  at  work.  The  tuning 
handle  is  turned  a  little  more,  and  a  peculiar  moaning 
sound  is  heard.  Turned  still  more,  the  sound  becomes 
a  weak  voice  or  music,  and  a  final  turning  of  the  handle 
brings  in  the  radio-phone  loud  and  clear.  The  tuning  is 
exceedingly  sharp.  A  slight  turn  one  way  or  the  other 
throws  out  the  radio^phone  altogether. 

The  author,  using  a  60-foot  wire  as  an  aerial,  running 
between  the  second  floor  of  his  house  and  a  large  tree, 
has  been  listening  to  the  Newark  broadcasting  station 
evening  after  'evening.  In  an  airline,  some  forty  miles 
separate  him  from  the  WJZ  station,  yet  the  radio-phone 
comes  in  loud  and  clear,  using  the  vacuum  tube  detector 
only.  With  one  stage  of  amplification,  the  sound  is  greatly 
increased,  and  with  two  stages  it  becomes  possible  to  use 
a  loud-speaker  so  that  the  radio-phone  is  to  all  intents 
and  purposes  on  a  par  with  the  phonograph,  and  the  head- 
phones become  unnecessary.  Still  more  remarkable,  with 
certain  atmospheric  conditions  it  is  possible  to  pick  up  the 
Pittsburgh  radio-phone  station  just  as  loud  as  Newark, 
although  under  normal  conditions  Pittsburgh  is  only  a 
trifle  as  loud  as  the  nearest  station. 

It  is  well  to  mention  here  that  the  radio-phone  receiver 


72  RADIO  FOR  EVERYBODY 

is  subject  to  that  bete  noir  which  is  dreaded  by  all  radio 
men,  namely,  static,  or  atmospheric  electricity.  Static 
asserts  itself  by  making  all  kinds  of  noises  in  the  telephone 
receivers,  ranging  all  the  way  from  a  frying  sound  to  a 
loud  scratch,  which  are  most  disagreeable  and  interfere 
materially  with  the  radio-phone  service.  During  the 
winter,  the  static  is  almost  negligible,  this  being  especially 
true  during  cold,  dry  winter  nights.  During  the  summer, 
however,  especially  with  the  super-sensitive  radio  receiv- 
ing sets  now  employed,  static  is  quite  troublesome,  al- 
though it  is  seldom  sufficiently  heavy  to  break  up  the 
radio-phone  reception  altogether. 

The  radio-phone  is  one  of  the  greatest  inventions  of 
the  age.  It  brings  right  into  our  homes  the  very  informa- 
tion which  we  desire,  and  the  best  there  is  in  music.  Not 
so  long  ago  an  entire  musical  comedy  was  broadcasted, 
and  the  listener  could  almost  visualize  the  performance. 
Even  the  dances  were  broadcasted,  the  actors  wearing 
special  shoes  so  that  the  sounds  of  their  dancing  could 
be  transmitted.  Imagine  what  the  radio-phone  means 
to  the  farmer,  far  removed  from  the  city,  yet  at  last  in 
daily  touch  with  the  metropolis !  And  there  are  many 
others  who  know  or  should  know  how  the  radio-phone 
now  makes  life  more  interesting  and  more  enjoyable. 


Chapter  III. 

DOT-AND-DASH  BROADCASTING 

FROM  MARKET  NEWS  TO 

TIME  SIGNALS 


TO  the  layman,  of  course,  the  radio-phone  broadcast- 
ing is  the  only  thing  that  counts.  The  dots  and 
dashes  that  are  picked  up  are  meaningless.  It  may  be 
interesting  to  note  the  different  kinds  of  radio  telegraph 
transmitters  that  can  be  picked  out  of  the  air;  perhaps 
there  is  some  interest  in  noting  their  relative  strength : 
but  from  a  truly  practical  standpoint,  they  have  little 
value  to  the  layman  who  has  not  as  yet  mastered  the 
telegraph  code. 

However,  aside  from  the  radio-phone  broadcasting 
service,  there  is  an  excellent  radio  telegraph  broadcasting 
service  now  available  in  practically  every  part  of  the 
United  States.  It  is  known  as  the  radio  market  news 
service  of  the  United  States  Bureau  of  Markets  and  Crop 
Estimates  and  represents  an  effort  on  the  part  of  the 
Bureau  to  make  its  market  news  more  immediately  avail- 
able and  more  effective  than  it  can  be  made  in  any  other 
way.  Ever  since  the  inauguration  of  the  first  market  news 
service  on  fruits  and  vegetables  in  May,  1915,  the  special- 
ists of  the  Bureau  have  given  continuous  study  to  the 
problem  of  supplying  market  news  on  agricultural  com- 
modities to  those  who  may  have  use  for  such  information 
as  quickly  as  possible  after  it  can  be  obtained.  The 
market  news  services  of  the  Bureau  cover  live  stock  and 
meats ;  dairy  and  poultry  products ;  fruits  and  vegetables ; 


74  RADIO  FOR  EVERYBODY 

hay,  feed  and  seeds,  and  some  other  commodities  asso- 
ciated with  these  four  general  groups.  The  information 
is  suppHed  to  and  is  utilized  by  producers,  shippers, 
dealers,  brokers  and  commission  men,  manufacturers, 
warehousemen,  demonstration  and  extension  workers, 
banks,  transportation  agencies,  chamber  of  commerce,  buy- 
ing and  selling  organizations,  and  other  commercial,  exten- 
sion and  educational  agencies. 

Getting  the  News  to  the  Public 

It  is  the  function  of  the  Bureau  of  Markets  and  Crop 
Estimates  to  gather  or  assemble  market  information  from 
reliable  sources  and  distribute  it  in  such  a  way  as  to  make 
it  available  to  the  greatest  possible  number  who  wish  to 
use  it.  In  performing  this  function  it  utilizes  and  co- 
operates with  all  agencies  possible.  It  affiliates  with  State 
agencies  which  may  or  may  not  have  similar  functions  with 
respect  to  the  State  as  the  United  States  Bureau  of  Mar- 
kets and  Crop  Estimates  has  to  the  Federal  Government. 
It  utihzes  the  railroads  for  information  relative  to  ship- 
ments and  movements.  In  one  way  or  another,  it  assem- 
bles information  from  every  available  source  where  such 
information  can  be  obtained. 

In  utilizing  radio  communication  as  a  means  of  dis- 
seminating crop  and  market  information,  the  Bureau  of 
Markets  and  Crop  Estimates  -is  taking  advantage  of  one 
of  the  agencies  which  has  certain  possibilities  possessed 
by  none  that  has  been  used  in  the  past.  This  new  method 
makes  it  possible  for  all  who  wish  this  information  to  help 
themselves  to  it,  if  they  will  but  equip  themselves  to 
receive  it  in  the  form  in  which  it  is  sent.  The  advantages 
of  broadcasting  information  by  radio  are  (1)  that  the 
information  can  be  intercepted  or  coj>ied  by  means  of  suit- 
able equipment  at  any  point  within  certain  approximate 
limits,  whether  or  not  such  point  is  connected  by  railroad, 
itelegraph  or  any  other  of  the  ordinary  means  of  communi- 
cation, and  (2)  that  the  transmission  of  the  news  is 
instantaneous.  These  two  factors  in  radio  communication 
make  it  possible  for  any  one,  whether  he  is  located  in  a 


RADIO  FOR  EVERYBODY  75 

congested  city  or  in  the  country  a  hundred  miles  from 
the  railroad  or  telegraph  wire,  to  receive  the  information 
with  equal  dispatch.  Radio  transmission  can  be  effected 
either  by  the  international  telegraph  code,  using  dots  and 
dashes,  or  by  radio-phone.  The  radio-phone  will  probably 
present  the  most  good  to  the  greatest  number.  For  the 
present,  and  for  some  time  to  come,  so  it  seems,  the  radio 
telegraph  mostly  is  used  for  this  work.  This  necessitates, 
for  the  time  being,  at  least,  a  knowledge  of  the  Continental 
telegraph  code,  which  can  be  readily  acquired  if  one  is  but 
willing  to  aevote  a  few  months  to  intense  study  and  prac- 
tice. In  another  chapter  we  shall  have  more  to  say  regard- 
ing the  code  and  how  it  can  be  mastered. 

Getting  the  Crop  and  Market  Reports 

Crop  and  market  reports  sent  out  broadcast  by  radio 
can  be  received  by  any  agency  having  suitable  equipment. 
With  the  development  of  broadcasting  by  radio-phone, 
there  is  sure  to  be  a  demand  for  receiving  equipment 
from  many  sources.  Not  much  greater  technical  knowl- 
edge will  be  required  to  receive  the  reports  by  radio  than 
to  use  an  ordinary  telephone. 

In  general,  at  present  the  broadcasted  reports  are  being 
utilized  by  various  marketing  agencies  in  giving  to  farmers 
the  national  crop  and  market  reports  combined  with  local 
market  information  which  is  distributed  in  other  ways, 
by  county  farm  organizations  or  other  local  agricultural 
agencies  acting  as  centers  of  information  for  the  county 
or  locality,  and  by  banks,  shipping  associations,  commer- 
cial exchanges,  commercial  clubs  and  newspapers,  all  of 
which  may  serve  as  agencies  for  secondary  distribution  of 
the  reports.  In  addition,  the  reports  may  be  received 
direct  by  farmers,  country  elevators,  dealers,  shippers,  and 
many  others  who  will  use  the  information  in  the  transac- 
tion of  their  business.  The  extent  to  which  this  latter  class 
will  receive  market  reports  direct  remains  to  be  seen.  It 
is  certain,  however,  that  the  State  and  county  radio  receiv- 
ing stations  will  be  developed  rapidly  because  of  the 
economical  reception  and  distribution  of  crop  and  market 


76  RADIO  FOR  EVERY-BODY 

reports  through  them.  Certain  individuals  or  a  small 
group  of  individuals  may  find  it  advantageous  to  solicit 
the  aid  of  radio  arnateurs  in  the  community.  This  should 
be  arranged  for  very  carefully  to  ensure  that  the  amateur 
is  capable  of  receiving  a  true  copy  of  the  reports  as  broad- 
casted. 

The  Radio  Market  News  Service  in  the  Making 

Since  the  radio  market  news  service  was  begun  experi- 
mentally by  the  United  States  Bureau  of  Markets,  on 
December  15,  1920,  it  has  developed  very  rapidly,  so  that 
at  the  present  time  the  national  market  news  is  not  only 
being  distributed  by  the  United  States  Bureau  of  Markets 
and  Crop  Estimates,  but  other  agencies  are  extending  the 
distribution  of  the  national  crop  and  market  reports  as  well 
as  local  market  reports.  The  service  was  started  by  the 
United  States  Bureau  of  Markets  at  Washington,  on  the 
date  already  mentioned.  One  report  was  sent  out  at  5  :00 
p.  m.  each  day  from  that  station.  This  was  continued 
for  four  months  to  determine  the  practicability  of  the 
method.  When  it  became  apparent  that  this  method  would 
not  only  be  practical  but  also  more  economical  and  efficient 
for  certain  kinds  of  distribution  than  any  other  agency, 
the  Bureau  of  Markets  took  up  the  matter  with  the  Post 
Office  Department  and  accepted  their  offer  to  utilize  the 
radio  stations  of  the  Air  Mail  Service  in  the  dissemination 
of  crop  and  market  reports.  At  the  present  time,  the 
larger  part  of  the  radio  market  news  service  of  the  Bureau 
is  handled  through  the  Post  Office  radio  stations.  Many 
of  the  agricultural  colleges  giving  instruction  in  radio 
communication  in  connection  with  their  departments  of 
physics  or  electrical  engineering,  either  alone  or  in  co- 
operation with  the  State  marketing  agencies,  have  set  up 
programs  of  broadcasting.  These  began  with  the  dis- 
semination of  weather  reports  from  the  Kansas  State 
Agricultural  College  in  1916.  Crop  and  market  reports 
are  now  being  broadcasted  frorrj  several  other  colleges. 
Some  privately  owned  stations  are  also  broadcasting  the 
information  by  radio-phone  or  by  radio  telegraph. 


RADIO  FOR  EVERYBODY  77 

The  map  on  page  <9  shows  the  location  of  the  stations 
now  broadcasting.  The  leased  wire  connections  of  the 
Federal  Bureau  are  also  shown.  The  leased  wire  service 
of  the  Bureau  of  Markets  and  Crop  Estimates  was  estab- 
lished in  1916  and  during  the  past  six  years  as  many  as 
17,600  miles  of  leased  wire  and  61  branch  offices  have 
been  in  operation.  The  leased  wire  has  been  used  to  carry 
reports  from  the  markets,  shipment  information  and  re- 
ports from  shipping  points  as  to  supply  and  demand,  and 
f .  0.  b.  prices.  Even  in  its  most  extended  form,  the  leased 
wire  with  the  largest  number  of  branch  offices  was  never 
able  to  reach  more  than  a  small  percentage  of  the  people 
interested. 

The  function  of  the  leased  wire  will  not  be  changed  or 
curtailed  by  the  establishment  of  the  radio  method,  but 
will  still  be  the  nucleus  of  an  effective  system  employing 
wired  telegraph  and  telephone  as  well  as  radio  telegraph 
and  telephone. 

The  Air  Mail  Radio  Service  of  the  Post  Office  Depart- 
ment was  estabHshed  primarily  to  give  communication 
between  the  flying  fields,  in  connection  with  the  transpor- 
tation of  mail  by  airplanes.  These  stations  have  to  be 
available  for  service  a  large  part  of  the  day  but  have  con- 
siderable time  which  is  not  necessarily  occupied  in  the 
business  of  the  mail  service.  The  market  reports  are  sent 
out  on  schedules  which  are  adapted  to  the  unoccupied 
time  at  the  stations.  This  incurs  merely  a  nominal  ex- 
pense to  the  Post  Office  Department  and  inasmuch  as 
the  market  information  is  obtained  for  other  uses  by  the 
United  States  Bureau  of  Markets  and  Crop  Estimates, 
the  service  as  constituted  at  present  incurs  practically  no 
additional  expense  to  this  Bureau.  Because  of  the  neces- 
sity of  using  stations  not  intended  primarily  for  broadcast 
transmission  but  rather  for  interstation  traffic  it  is  not 
possible  to  organize  as  effective  and  complete  a  service 
as  could  be  furnished  by  a  chain  of  stations  equipped 
solely  for  radio  broadcast  transmission.  It  is  thought 
desirable,  however,  to  take  advantage  of  every  facility 
at  hand  in  order  to  obtain  experience  in  handling  market 


78  RADIO  FOR  EVERYBODY 

news  by  this  method  and  be  ready  to  install  a  more  effec- 
tive service  shouild  special  facilities  be  made  available  at 
a  later  date. 

The  Form  of  Crop  and  Market  Reports 

Certain  types  of  market  information  can  be  put  into  a 
form  for  rapid  transmission  by  use  of  standard  forms 
and  code  letters.  This  does  not  involve  the  ordinary  use 
of  code  words  and  the  necessity  of  coding  and  decoding 
the  messages  received,  but  it  does  make  necessary  the  send- 
ing and  receiving  of  the  reports  on  special  forms.  Inas^ 
much  as  the  sender  and  the  receiver  use  identical  forms,  it 
is  possible  by  the  use  of  code  letters  preceding  each  blank 
space  in  which  information  is  to  be  copied,  to  transmit 
rapidly  a  large  amount  of  information  prepared  in  stan- 
dardized form.  By  the  use  of  such  special  forms  and 
regular  transmitting  schedules  a  very  effective  service  can 
be  developed.  This  field  has  only  been  touched  upon  and 
great  improvements  undoubtedly  will  be  developed  in  the 
handling  of  information  in  this  way. 

The  receiving  of  reports  by  telegraph  codes,  using  dots 
and  dashes,  makes  it  necessary  that  receiving  operators 
understand  the  international  (Continental)  code  and  be 
able  to  copy  at  least  15  words  a  minute.  Wherever  radio 
telephone  communication  is  established,  it  is  necessary 
only  that  the  operator  be  able  to  adjust  the  radio  receiving 
equipment  properly,  since  the  telephone  reports  are  repro- 
duced in  the  radio  receiving  equipment  just  as  they  would 
be  in  a  wall  or  desk  telephone.  Wherever  it  is  desired 
to  utilize  the  reports  sent  out  by  radio  telephone,  for  pub- 
lication or  further  distribution,  they  can  be  received  and 
copied  by  a  stenographer.  At  the  present  time  only  a  few 
special  forms  of  reports  have  been  developed  for  use  in 
radio  broadcast  communication.  Others  will  be  developed 
from  time  to  time  as  the  service  grows  and  modifications 
of  the  present  forms  undoubtedly  will  be  made. 

In  the  forms  already  in  use.  two-letter  code  symbols 
are  used  to  designate  the  information  sent.  These  are  used 
in  two  different  ways :     (1)  A  two-letter  symbol  is  placed 


80  RADIO  FOR  EVERYBODY 

at  the  beginning  of  the  blank  space  which  is  to  contain 
a  certain  type  of  information.  The  operator  simply  sends 
the  two  code  letters  and  the  information  occupying  the 
blank  space.  For  example,  in  sending  ''New  Jersey  sacked 
Irish  Cobbler  potatoes  per  100  lbs.  in  consuming  markets, 
New  York  (SR)  $1.75-2.10,"  the  operator  would  send 
only  "(SR)  $1.75-2.10."  Code  letters  are  also  used  to 
designate  certain  options  or  alternatives  to  indicate  types 
of  information.  For  example  "Demand  for  Wheat,  Mill- 
ing, Strong  (DK)  ,  Fair   (DL)  — ,  Poor   (DM) 

• ."    The  operator  would  send  (DK),  (DL),  or  (DM), 

as  indicating  one  of  the  three  alternatives  and  the  receiving 
operator  would  put  a  check  mark  in  the  blank  space  fol- 
lowing the  letters  received.  Fractions  are  avoided  wher- 
ever possible,  but  when  necessarv  are  sent  as  f  oHov^s : 

$1.50  Is  sent  as  1R50. 

$1.5014  is  sent  as  1R50  and  1  DN  2. 

^  of  1  cent  is  sent  as  7  DN  8  cents. 

G5J^  cents  is  sent  as  65  and  7  DN  8  cents. 
All  this,   it  will  be  noted,   is   to  avoid  confusion  and 
error,  for  if  there  should  be  any  doubt  about  the  figures, 
it  goes  without  saying  that  the  entire  value  of  the  reports 
would  be  rendered  worthless. 

A  Question  of  Co-operation 

A  number  of  States,  through  State  bureaus  of  markets 
and  State  extension  departments,  are  co-operating  wi/th 
the  Federal  Bureau  of  Markets  and  Crop  Estimates  in 
organizing  their  States  to  receive  and  utilize  radio  crop 
and  market  reports.  In  some  cases  they  have  established 
regular  information  centers  which  serve  as  distribution 
points  for  sending  out  the  information  through  other 
channels.  In  other  cases  progressive  agricultural  counties 
have  installed  receiving  equipment  in  connection  with 
farmers'  organizations  so  that  the  information  will  be 
available  to  the  county  agent  for  further  extension  either 
through  the  daily  newspapers,  telephone  exchanges,  or 
other  agencies.  For  the  present  it  is  probable  that  the 
larger   application  of   the   radio   service   will  be  through 


RADIO  FOR  EVERYBODY  ^  81 

organizations  or  institutions  which  will  obtain  operators 
and  equipment  to  receive  the  reports  and  distribute  them 
or  make  them  available  to  individuals  or  groups  or  organi- 
zations of  producers.  As  the  radio-phone  comes  into 
more  general  use,  many  of  those  engaged  in  producing  or 
marketing  farm  products  will  undoubtedly  obtain  equip- 
ment to  receive  the  reports  directly  as  no  special  trained 
operator  will  then  be  necessary.  In  several  States  radio- 
phone equipment  is  being  utilized  so  that  the  reports 
which  are  received  in  code  over  the  leased  wire  or  by 
wireless  may  be  re-transmitted  by  radio-phone  for  the 
benefit  of  producers  in  the  State. 

There  are  many  technical  problems  in  connection  with 
radio  telegraphy  and  radio  telephony  that  have  to  be  con- 
sidered in  the  dissemination  of  broadcast  reports.  The 
questions  of  wave  length  and  kind  of  transmission  are  both 
very  important.  Although  the  amateurs  are  restricted  to 
the  use  of  200  meters  or  less  for  transmission,  a  large 
percentage  of  them  are  equipped  to  receive  messages  over 
a  much  wider  range  of  wave  lengths.  Questionnaires 
sent  to  a  limited  number  of  amateurs  having  radio  trans- 
mitting sets  show  that  about  50  per  cent  are  now  equipped 
to  receive  messages  transmitted  on  wave  lengths  between 
150  and  3000  meters.  At  first  thought  it  would  seem 
best  to  have  the  market  reports  transmitted  on  a  short 
wave,  but  the  lower  wave  lengths  lack  carrying  power. 
The  shorter  waves  have  additional  objections  owing  to 
interference.  Since  amateurs  are  licensed  to  transmit  on 
the  shorter  waves,  it  would  be  very  difificult  for  the  one 
receiving  market  news  to  get  solid  copy — a  comp'lete  and 
accurate  copy  of  the  message  as  sent — if  several  nearby 
amateurs  were  transmitting  at  the  time  the  Post  Office 
station  was  transmitting.  Because  of  the  greater  trans- 
mitting range  and  the  decreased  interference,  wave  lengths 
of  2500,  3000  and  4000  meters  are  being  used  at  the 
present  time. 

The  stations  from  which  the  market  reports  are  now- 
being  sent  by  radio,  the  type  of  transmitting  sets,  the  wave 
lengths  used,  and  the  time  at  which  the  several  reports  are 
sent  are  given  in  the  transmitting  schedule  that  follows : 


OS 


ri 


0:= 


<i  t; 

O 


o 

fin 


8 


dd 

O  CO 


o  o 

CO  O 


23 

>  ^ 
c3    c« 


c3    3 


(fl 

tfl 

Ui 

^ 

;-i 

^ 

a 

^ 

& 

a 

a 

gi 

g 

8 

^5 

3 

3 

lO 

:3 

'»-' 

CM 

N— ' 

a> 

s  a  s  s  s 

a  a 

OJ 

a  a  a  a  a  a  a"  a 

s 

rt  d  a  a  D, 

dd 

a 

rj  d  dddddp 

H 

lo  O  O  O  O 

\o  vo 

'c3 

loOOO^^^oioir) 

13 

•Tf  CO  CO  CO  CO 
O^    T-M    (Nl    (NJ    CO 

4f  Tf 

Ti  <rj  TJ  TJ  n  "^  71  ■?; 

0\i-trq»-<CMTJ-X^X^ 

*-c 

;^ 

1— I    T-H 

1 

6  6  6  6  6 

CO  O  O  O  O 

O^    »-H    C<l    <N    CO 

^8888^8^ 

0^»-ir<iTH«Nirj-i^r^ 

1-4    T-4 

t-t  i-< 

c«    c/: 

en    03    en 

^  o  o  o  ^ 

C«      CO 

-_  _  »—  .»^    ^    1/2    t« 
cmOOOO    qj    (u    cl 

Tt    CN)    CNl    ^    \0 

'^csirofM'^f-iJ-i*- 

. 

^           ^ 

u            o 

•d 

o            o 

^-^."^       rt 

^-^ 

^^  ^^^      ^oo    ^ 

o  o 

0,0  -id    ^,           «-^    «,  -^ 

o  +-> 

•iir  o  «->  S^       o  45  <-> 

+->  C/2 

(u  ^  o  >      *-.  >  o 

^^o^Sg 

^^ 

^c/3-;3      xn-^^ 

p^^.^o£ 

S  >-^ 

^•n.^ 
-^o-^ 

ii  p^  3  c  c 

^  ^°.a.g 

OJ    O  1— 1    o    u 

Co  »*-<      rn      C      Cu      r/1  "T^ 

QJ   u   03   c  "r^   <->  C    "5 

.>2artS:a§a 

o 

xi 

5 
O 

g 

o 

b 

< 

fc^ 

fc4 

■ 

o 

O 

I 

r^o 

3 

fa 

n 

o 

fV'' 

O 
<-t 

B 

1 

n' 

w 

o 

fD 

O  O    ">    Q 

£,Q-p  Ef5- 
>-«    ^    .-    o 


5'  p 

'3^   S 


o  S  '^  cr 

0.<  o  i:^ 

3  O 

M    S  f^ 

•     Q-  re  p 


n 


o 


7i 

pi 

^ 

2; 

71 

1 

r 

O 

0 

H 

1 

C/3 

s 

s 

K 

:2: 

H-4 

1 

^ 

:^ 

^ 

:^ 

«j 

(D 

ftj 

v; 

m 

<^ 

< 

< 

o 

cr 

3:5:<* 

n  r>  CD 

pi  ^  n  n  O) 

3  ^  3!5t<' 

P   ^   n'  n   re 

^ 

P 

p  p  . 

rr  ^  P  P 
p  ^  crq  org  C/3 

g'^:^c^  C/5 

» 

7Q    O) 

crq  (jq  O) 

r<. 

o  ^ 

o  o  j:r 

'^        O  O  ?r 

O    O    JIJ" 

S 

C& 

rr| 

CSCC& 

?SceI 

< 

<    <    ^ 

^  *<  <  <  ^ 

TO   '<i    <    <     _ 

ro   >cl 

ft>    fD    ^ 

.^^™  ^  ^ 

rih^"'      ""      /'^ 

C/^R 

^^n 

^V.^^^ 

^^CT^C/^S^ 

>3 

'"'"    ft! 

O    <     ri-   ^-^   o 

o   <   <-^  <-^  ro 

►^ 

O    ►i- 

o  o  2. 

n  ^  o  o  ►4. 

n  r5  o  o   «. 

\i- 

o  XJ 

0   0*0 

t^""   o  n  "O 

►rr       o  o  -u 

0 

t^sr 

^?rj^ 

ST 

^ 

hj^^ 

'T3  't^'tJ  , 

^^ 

K)  -P>- 

«-«     KJ   4^ 

1-t    -(    -(    to  4^ 

kT  i-T  >-«  t^J  45. 

(T-'  <0 

o  t^ 

C/2 

ro   fi>   a>   o  "^ 

CP     C/2     W) 

ill 

S-i 

I-* 

o 

3 

I-' 

h-  O 

-t^  tsj  00 

00  00  4^  K)  \0 

00  00  C/l  to  O 

88 

s 

8SS 

^ 
p 

§8§88 

^888§ 

3 

? 

1     1 

5^ 

o 

H 
3 

1      1      1 

3^ 

1  1  J  1  I 

3 

1  1  1  1  1 

>-« 

s  i 

4^  to  00 

o 

H 
3 

00  OO  4^  to  vO 

P 

00  00  en  to  o 

EL 
H 
3 

'^\^'^(J^'^ 

4L  "hi  "hI  o^  4I 

en,  O  <-ri 

Ca  Cn  Cfi  O  cyi 

"O  t3  XJ  TD  P 

3 

cyi  Cn.  en.  0  en 

TJ  "O  XJ  'O   P 

3  3 

CD 

3  3  3 

ft 

3  3  3  3  3 

3  3  3  3  3 

fn 

s 

CO 

_^_^ 

OJ 

Co 

^ 

3 

3 

O 

3 

3 

§ 

3^ 

3 
3 

0 

2^ 

3  ^ 

O 

3 

3  ?5 

3 

^P 

3  n 

g 

CLP 

|3 

1 

I 

ft) 
S5 

SI 

1 

1 

s 

84  RADIO  FOR  EVERYBODY 

The  arc  stations,  it  is  interesting  to  note,  usually  have 
a  greater  transmission  range  than  the  spark  stations. 
Furthermore,  it  should  be  borne  in  mind  that  spark  stations 
transmit  damped  waves  and  the  arc  stations  transmit  un- 
damped or  continuous  waves.  This  information  is  neces- 
sary for  the  selection  of  the  proper  receiving  sets,  and 
more  will  be  said  about  this  matter  in  the  chapter  on  re- 
ceiving apparatus. 

Why  Radio  Telegraphy  is  Used  at  Present 

The  subject  of  radio  telegraph  and  radio  telephone 
transmission  has  been  touched  upon  before.  All  things 
being  equal  and  in  readiness,  radio  telephone  transmission 
would  be  the  logical  method  to  use.  At  present,  however, 
it  might  be  quite  difficult  to  purchase  reliable,  hig^h^power 
radio  telephone  equipment  on  the  commercial  market,  so 
claim  the  authorities ;  furthermore,  if  the  Bureau  of  Mar- 
kets and  Crop  Estimates  had  waited  until  the  high-power 
telephone  transmitter  had  become  commercially  available 
it  would  not  have  made  the  year  or  more  of  gratifying 
history  which  the  service  now  has.  After  the  broadcasting 
of  market  news  by  radio  telegraph  was  shown  to  be  prac- 
tical it  was  decided  to  use  the  radio  transmitting  stations 
of  the  Air  Mail  Service  which  were  already  installed  and 
in  operation.  This  forms  the  first  chain  of  information- 
disseminating  radio  stations  without  the  delay  and  cost  of 
constructing  new  ones.  It  is  probable  that  these  and  other 
like  ones  will  remain  the  master  stations  for  some  time. 

Furthermore,  when  the  Bureau  of  Markets  and  Crop 
Estimates  is  successful  in  its  work  of  getting  the  various 
States,  country  and  private  organizations  to  equip  them- 
selves to  receive  the  radio  telegraph  market  reports,  great 
advancement  will  have  been  made,  for  those  stations  will 
be  ready  to  rebroadcast  the  reports  by  radio  telephone 
when  that  system  can  be  installed.  In  other  words,  a  radio 
receiving  station  that  will  pick  up  the  telegraph  messages 
from  the  ether  will,  without  any  alteration,  pick  up  the 
radio  telephone  messages  as  well. 


RADIO  FOR  EVERYBODY  85 

The  Bureau  of  ^larkets  and  Crop  Estimates  is  under- 
taking to  establish  on  an  efficient  basis  the  radio  market 
news  serwce.  There  undoubtedly  are  many  obstacles  in 
the  way  of  making  it  an  immediate,  complete  success,  but 
so  far  as  these  have  been  considered  up  to  the  present  time, 
they  are  not  insurmountable  and  it  is  thought  that  with 
the  radio  operators  located  over  the  country  who  are  trying 
to  receive  the  reports,  it  may  well  be  that  the  Bureau  will 
be  able  in  a  very  short  time  to  put  the  service  on  an  entirely 
practical,  substantial  basis. 

At  the  present  time  the  Bureau  is  entirely  dependent 
upon  the  co-operation  of  the  Post  Office  Department  in 
the  dissemination  of  the  reports  and  they  are  giving  their 
heartiest  assistance  to  the  Bureau  in  this  work.  It  wil'l  be 
some  time  before  receiving  stations  will  be  distributed  all 
over  the  country,  receiving  the  reports  regularly.  A  great 
many  of  the  licensed  amateur  operators  are  receiving  the 
reports  and  many  of  them  are  fully  competent  to  do  this. 
However,  it  cannot  be  considered  as  on  a  permanent  basis 
until  the  State  and  county  agencies  have  made  provision 
for  equipment  and  regular  operators  to  receive  the  reports 
regularly.  These  are  all  controllable  factors.  The  ap- 
parently uncontrollable  factor  which  must  be  given  con- 
sideration is  the  one  of  natural  conditions,  such  as  weather, 
strays  and  dust  storms.  These  will  be  real  obstacles,  which 
in  some  localities  and  in  some  seasons  will  be  found  worse 
than  in  others,  During  midsummer,  radio  reception  during 
daylight  hours  may  be  frequently  interrupted.  In  fact,  it 
'may  be  impossible  to  receive  the  reports  at  times. 

It  will  not  be  necessary  for  our  immediate  needs  to 
discuss  the  probable  reasons  for  these  peculiar  atmospheric 
conditions  which  interfere  with  radio  reception.  It  is  a 
fact,  however,  that  frequently  during  the  summer  months, 
the  strays  may  completely  drown  out  the  radio  signals 
picked  up  by  the  receiving  set.  The  idea  that  higher 
amplification  will  relieve  the  situation  is  erroneous.  The 
amplifier  usually  amplifies  the  strays  along  with  the  in- 
coming signal,  so  the  amplified  signal  is  often  less  intel- 
ligible than  the  signal  received  on  a  simple  detector.    The 


86  RADIO  FOR  EVERYBODY 

use  of  high-power  transmitting  stations  is  an  advantage 
in  this  respect. 

During  storms  it  sometimes  is  not  only  impossible  to 
receive  any  messages,  but  it  may  be  unwise,  especially  if 
the  storm  is  accompanied  by  lightning  discharges.  At  such 
times  the  antenna  should  be  grounded  to  protect  the  ap- 
paratus and  no  attempt  made  to  receive  radio  messages. 
Although  dust  storms  are  not  generally  prevalent,  they  are 
to  be  reckoned  with.  Occasionally  -the  transmitting  range 
of  a  station  will  be  limited  in  a  certain  direction  owing 
to  an  intercepting  dust  storm.  There  are  yet  other  diffi- 
culties, such  as  fading  of  signals,  which  must  be  encoun- 
tered, but  some  of  these  are  avoided  by  using  the  long 

SSSFM     lo"  zo'  so"  ^'  fo'  js' 

••••••• •••••••••••••••••••••©•••••••••« •••»»«# «««»«««»ocooo 

****•*••••••••••• •••••••••••^•••••••» ••••••••••••••• ••ooooo 

••••••••••••••••••••••••••••©••••••••••####««#»«««0»00OOOOO 

S3* 

••••••••••••••••• ••»«««««#«»o« ••••••••• •••••«»«««oooooooooo 

tZMoon 

lOP./ft.  ^,  ^  -, 

mmoooo      J^«     ^      /?. 

Diagrrammatic  explanation  of  the  official  Navy  time  sig:nals  as  sent 
out  by  the  Arlington  station.  These  sigrnals  are  re-transmitted  by 
several  of  the  broadcasting  stations.  £ach  black  dot  represents  a 
transmitted  dot,  while  the  white  dots  represent  spaces.  The  time 
signals  start  five  minutes  before  12  o'clock  noon  and  10  o'clock  P.  M. 
and  follow  the  schedule  here  depicted,  terminating  with  a  dash 
on    the    hour,    followed    by    a    four    dot    space    and    the    call    letters 

'•N  A  A." 

waves.  However,  after  taking  all  of  these  things  into 
consideraftion  it  is  quite  probable  that  a  high  percentage 
of  completeness  may  be  anticipated  in  handling  this  kind 
of  service. 

From  General  News  to  Time  Signals 

Then  there  are  other  radio  telegraph  broadcasting  serv- 
ices available  to  the  owner  of  a  receiving  set.  The  most 
important  of  these  is  the  broadcasting  of  time  signals  and 


RADIO  FOR  EVERYBODY  87 

weather  bulletins  by  the  high  power  naval  station  at 
Arlington,  Va.  The  time  signals  and  weather  bulletins  are 
sent  out  twice  daily  on  a  wave  length  of  2500  meters,  at 
11.55  a.  m.  and  9.55  p.  m.  The  signals  begin  at  these 
times  and  the  final  dash  is  sent  at  12  noon  and  10  p.  m. 
and  are  astronomically  correct  for  the  meridian  of  75 
degrees  west  of  Greenwich. 

The  signals  are  sent  out  as  follows :  Beginning  at  11.55 
a.  m.  or  9.55  p.  m.  a  dot  is  sent  every  second  for  the  first 
thirty  seconds,  then  one  second  is  skipped,  and  beginning 
with  the  thirty-first  second  to  the  fifty-fifth  second  the 
dots  are  again  sent,  one  each  second.  The  last  five  seconds 
of  the  first  minute  are  skipped,  and  the  signals  begin 
again  at  exactly  the  beginning  of  the  fifty-sixth  minute. 
The  same  schedule  is  maintained  through  the  fifty-seventh 
and  fifty-eighth  minutes  right  through  until  the  fiftieth 
second  of  the  last  minute  is  attained.  Then  comes  a 
silence  or  blank  for  ten  seconds,  and  the  next  dash  is 
exactly  12  o'clock  noon  or  10  o'clock  in  the  evening,  as 
the  case  may  be.  The  general  scheme  of  the  time  signals 
is  perhaps  made  clearer  by  studying  the  accompanying 
chart.  This  time  is  absolutely  accurate  and  is  employed 
by  ships  at  sea  for  the  setting  of  chronometers,  and  by 
progressive  jewelers  and  others  desiring  an  accurate  time 
service.  The  signals  are  transmitted  at  Arlington,  to  be 
sure,  but  the  dots  originate  in  a  master  clock  at  the  Naval 
Observatory. 

No  sooner  are  the  time  signals  over  than  the  Arlington 
station  sends  out  .the  weather  bulletin  in  code — a  code, 
however,  Which  is  quite  simple  to  understand.    A  weather 
bulletin,  as  sent  out  by  Arlington,  runs  as  follows : 
QST  de  NAA,  USWB,  S01081— T02261— 
DB0251  —  HOOSM  —  C01261  —  K00441— 
P1242.      .. 
All  of  which  means,  when  reduced  to  plain  English, 
thait  the  letters  stand  for  K — Key  West,  Fla. ;  S — Sidney, 
Nova  Scotia;  T — ^Nantucket,  R.  I.;  DB — Delaware  Break- 
water ;  H — Cape  Hatter  as,  N.  C. ;  C — Charleston,  S.  C. ; 
P — Pensacola,  Fla. ;  B — Bermuda.    The  first  .three  figures 


88 


RADIO  FOR  EVERYBODY 


following  the  letter  are  the  barometer  reading  at  the 
various  places.  Taking  the  first  set  of  figures  sent  out, 
S01081,  the  figures  010  represent  the  barometer  reading 
of  30.10  inches,  and  the  next  figure  represents  the  direc- 

tion  of  the  wind,  which  hap- 
■j — ^^^^  pens  to  be  NW  in  this  case, 

^^/q  ^\N£         since  the  numerals  begin  with 

^^  1    for    North,    2    for    NE,    3 

for  E,  4  for  SE,  and  so  on, 
^^7  \  gjg       as  shown  in  the  accompanying 

diagram,    reading   around   the 
compass  in  the  same  direction 
^^  ^/SE         as  travel  the  hands  of  a  clock. 

J — ^"^  The   last   numeral   means   the 

^  velocity  of  the  wind,  and  the 

How  numerals  are  used  to  r    ^^        •  i.   'U^  '  i.u       c. 

indicate  the  points  of  the        followmg  table  gives  the  fig- 
thrH^.^^Jr^r^ft^-in"  T^*"        ures  and  their  values  in  statute 

the  direction  ot  wind  num-  .      ,        .-       . 

erais  used  in  the  ArUngton        miles  (1.15  uautical  miles)  per 

weather    bulletins.  In  • 

0 — Cairn 0  to  3  miles  per  hour 

1 — Light  air 8  miles  per  hour 

2 — Light  breezes  ...  13  miles  per  hour 

3 — Gentle  breezes  .  .  18  miles  per  hour 

4 — Moderate  breezes  23  miles  per  hour 

5 — Fresh  breezes ....  28  miles  per  hour 

G^Strong  breezes. .  .  34  miles  per  hour 

7 — Moderate  gale. .  .  40  miles  per  hour 

8— Fresh  gale 48  miles  per  hour 

9 — Strong  ga'le   ....  56  miles  per  hour 

10 — Whole  gale 65  miles  per  4iour 

11 — Storm   75  miles  per  hour 

12 — Hurricane  90  miles  per  hour 

Now,  therefore,  take  the  code  signal  K00441.  The  K, 
it  will  be  noted,  stands  for  Key__West ;  the  figure  004 
states  that  the  barometer  stands  at  30.04  inches ;  the  next 
figure  indicates  that  the  direction  of  the  wind  is  South 
East,  and  the  last  figure,  1,  i;epresents  the  velocity  of  the 


RADIO  FOR  EVERYBODY  89 

wind,  which  in  this  instance  is  light  air,  or  a  breeze  having 
a  velocity  of  only  eight  miles  an  hour. 

The  Arlington  time  signals  and  weather  bulletins  are 
sent  on  a  wave  length  of  2500  meters.  The  call  letters  of 
this  station  are  N  A  A,  which  are  signed  immediately 
after  the  final  dash  in  the  time  signals.  Fortunately,  the 
weather  bulletins  are  sent  at  a  slow,  even  speed,  so  that  a 
person  with  only  a  slight  training  in  the  telegraph  code 
can  copy  down  the  letters  and  figures.  It  is  well  to  men- 
tion here  that  the  bulletins  are  sent  out  by  automatic 
transmitter,  so  that  the  dots  and  dashes  are  perfectly 
formed. 

Certain  radio-phone  broadcasting  stations  give  out  the 
time  signals  by  radio-phone.  This  is  accomplished  by 
receiving  the  time  signals  from  Arlington  on  a  long-range 
receiving  set,  and  then  amplifying  these  signals  until  they 
are  sufficiently  loud  in  a  telephone  receiver  which  is  held 
up  to  the  transmitter  microphone  for  retransmission  via 
the  radio-phone.  In  this  manner  the  persons  in  the  vicinity 
of  the  radio-phone  broadcasting  station  can  receive  the 
time  signals  without  having  to  tune  up  to  the  long  wave 
length  of  the  Arlington  station.  Furthermore,  the  radio- 
phone broadcasting  stations  receive  the  weather  bulletins 
and  broadcast  them  In  plain  English,  which  requires,  of 
course,  absolutely  no  knowledge  of  the  telegraph  code. 

Time  signals  and  weather  bulletins  are  broadcasted  by 
other  naval  stations.  Thus  the  Great  Lakes  station  NAJ, 
transmitting  on  1512  meters,  sends  out  time  signals  at  10 
p.  m.  (90th  meridian  time).  Also,  North  Head,  Wash., 
San  Francisco,  Cal.,  and  San  Diego,  Cal.,  transmit  the 
time  signals  at  10  p.  m.  (120th  meridian  time),  followed 
by  the  weather  bulletins.  The  Pacific  coast  stations  broad- 
cast the  information  first  on  their  usual  working  wave 
length,  next  on  952  meters,  and  finally  on  600  meters. 
Reports  from  these  stations  are  preceded  by  "USWBSF,'* 
the  first  four  letters  standing  for  ''United  States  Weather 
Bureau"  and  the  last  two  for  San  Francisco. 

Weather  reports  from  the  Pacific  coast  stations  are 
broadcasted  at  8  a.  m.,  noon,  4  p.  m.,  and  8.00  p.  m.    Cape 


90  RADIO  FOR  EVERYBODY 

Blanco  broadcasts  Tatoosh,  N'orth  Head  and  Eureka 
weather  after  local  report.  At  8  a.  m.  and  8  p.  m.  Eureka 
broadcasts  the  6  a.  m.  and  6  p.  m.  weather  conditions  at 
Farallones;  Farallones,  in  turn,  broadcasts  the  6  a.  m. 
and  6  p.  m.  weather  condftions  at  Eureka,  and  7  a.  m. 
and  7  p.  m.  weather  conditions  at  the  Farallones. 

Aside   from   the   Atlantic  coast   abbreviations   already 
given,  the  following  are  also  necessary: 
Great  Lake  Region 

Duluth  DU 

Marquette    M 

Sault  Ste.  Marie U 

Green  Bay G 

Chicago CH 

Alpena L 

Detroit D 

Cleveland V 

Buffalo ...     F 

Pacific  Coast  Region 

Tatoosh T 

North  Head .     NH 

Eureka E 

San  Francisco SF 

San  Diego SD 

Aside  from  the  time  signals  and  weather  bulletins,  there 
are  various  press  broadcasting  services  operating  from 
time  to  time.  Some  of  these  have  the  amateur  very  much 
in  mind,  and  in  consequence  transmit  the  press  items  at  a 
slow  rate  of  speed.  AH  in  all,  there  is  quite  as  much 
interesting  news  and  general  information  to  be  obtained 
through  the  radio  telegraph  broadcasting  as  there  is  by 
radio^phone,  although  it  goes  without  saying  that  the  first 
can  be  received  by  any  one  without  training  of  any  kind, 
while  the  second  presupposes  at  least  a  working  knowledge 
of  the  dot-and-dash  language  of  the  telegraph. 

From  Radio  Telegraph  to  Radio-Phone 
As  this  is  being  written  word  comes  to  us  to  the  efifect 
that  Government  information  is  shortly  to  be  broadcasted 


RADIO  FOR  EVERYBODY  91 

by  radio-phone,  this  service  taking-  the  place  of  the  present 
radio  market  news  service  of  the  United  States  Bureau  of 
Markets  and  Crop  Estimates,  as  described  early  in  this 
chapter.  A  radio-phone  has  recently  been  installed  on  the 
top  floor  of  the  United  States  Post  Office  Building  in 
Washington,  D.  C,  and  sufficient  power  is  now  available 
to  broadcast  Governmental  messages  to  the  public  over  a 
wide  area.  Governmental  information — data  assembled 
by  the  various  departmental  bureaus  relating  to  farming, 
fruit-growing,  lumbering,  mining,  and  general  knowledge 
— is  being  distributed  throughout  the  United  States.  Con- 
gress is  being  urged  to  establish  a  "Bureau  of  Communi- 
cation" in  the  Post  Office  Department,  appropriating  $500,- 
000  annually  for  its  maintenance,  thus  designating  a  clear- 
ing house  for  the  broadcasting  of  knowledge  of  a  varying 
nature  by  radio,  catering  to  the  diverse  interests  of 
110,000,000  citizens. 

The  abandonment  of  radio  telegraphy  in  favor  of  radio- 
telephony  as  a  vehicle  for  the  transmission  of  weather  and 
market  information,  which  service  was  introduced  April 
15,  1921,  marks  the  advent  of  a  hitherto  unprecedented 
popularity  for  the  distribution  of  Governmental  data  by 
radio  communication.  Radio  telegraphy,  after  eight  and 
one-half  months  of  practical  app'lication,  proved  to  be  too 
specialized  in  nature,  involving,  as  it  does,  a  knowledge 
of  the  international  telegraph  code  for  use  as  a  medium 
of  circulating  wxather  forecasts  and  the  fluctuating  ten- 
dencies of  the  markets.  Hence  the  decision  to  adopt  radio 
telephony  as  the  distributing  vehicle,  the  operation  of  the 
radio-phone  being  little  more  complicated  than  the  use 
of  a  common  telephone,  a  sewing  machine,  or  phonograph. 
It  is  contemplated  that  instant  and  almost  universal  popu- 
larity will  be  accorded  the  latter  system. 

The  present  installation  in  the  Post  Office  Department 
Building  at  Washington  is  the  first  unit  of  its  kind  to 
be  placed  in  operation,  and  claims  to  novelty  may  be  ad- 
vanced with  regard  to  its  mechanism.  This  wireless 
telephone  puts  14  amperes  into  the  antenna  at  1160  meters 
wave  length,  which  is  a  goodly  amount  of  radio  energy,  as 
radio  transmitters  go.     The  modulation  of  the  voice  is 


92  RADIO  FOR  EVERYBODY 

said  to  approach  perfection.  Preliminary  tests  have  suc- 
ceeded in  flinging  the  voice,  so  to  speak,  as  far  west  as 
Bryan,  Ohio,  and  southward  to  Atlanta,  Georgia,  dis- 
tances exceeding  1,000  miles.  The  transmitter  is  quite 
flexible,  so  that  the  service  may  be  varied  to  suit  varying 
operating  conditions  if  necessary. 

Contingent  upon  the  will  of  Congress  in  appropriating 
the  requested  $500,000  for  estabhshment  of  a  "Bureau  of 
Communication,"  the  service  will  be  extended  in  its  reach 
as  well  as  expanded  in  nature.  Isolated  areas,  as  well  as 
frequented  points  in  the  United  States,  will  be  visited  by 
this  hurry-up  method  of  spreading  the  news.  At  present 
there  are  eight  radio  stations,  as  already  described,  orig- 
inally established  in  conjunction  with  the  transportation  of 
mail  by  airplane,  used  as  distributing  agencies  of  market 
and  weather  reports.  These  are  located  at  Washington, 
D.  C. ;  Cincinnati,  Ohio ;  Omaha  and  North  Platte,  Neb. ; 
Rock  Springs,  Wyo. ;  Blko  and  Reno,  Nev.  Radio-phone 
stations  in  prospect,  by  reason  of  the  expansion  of  the 
service,  will  be  located  in  Georgia,  Texas,  California,  Mon- 
tana, Illinois  and  at  some  point  in  the  New  England 
States.  A  survey  being  conducted  by  the  Post  Office 
Department  will  determine  the  exact  locations  of  these 
information-distributing  stations. 

The  Post  Office  Department  voices  the  belief  that  the 
widespread  dissemination  of  Governmental  knowledge  will 
not  only  prove  of  economical  value  to  a  varied  citizenry 
of  the  United  States,  but  will  serve  as  a  leavening  process 
in  Americanizing  the  increasing  element  of  foreign  popu- 
lation in  our  midst.  The  Post  Office  Department  will  not 
only  give  circulation  to  market  news  and  weather  fore- 
casts, in  the  event  that  Congress  sanctions  an  enlargement 
of  the  service,  but  the  different  Government  bureaus  will 
be  drawn  upon  for  facts  pertaining  to  discoveries  and 
developments  that  will  serve  the  diverse  interests  of  the 
farmer,  miner,  rancher,  fruit-grower,  forester  and  lumber- 
man. Then,  too,  the  public  in  general  can  appropriate  to 
advantage  much  of  the  information  circulating  through 
space  by  reason  of  its  practical  value  and  entertaining 
quality. 


Chapter  IV. 

RECEIVING   EQUIPMENT  AND  THE 
INTERCEPTION  OF  RADIO  WAVES 


THERE  is  nothing  complicated  about  radio  reception. 
The  apparatus  may  be  of  the  simplest  sort,  if  the 
distance  to  be  spanned  is  relatively  small ;  virtually  no 
experience  is  required,  for  anyone  can  turn  the  few- 
knobs  and  adjust  the  detector;  no  licenses  are  required, 
and  anyone  can  intercept  radio  waves  without  formality 
of  any  kind ;  and  the  cost  is  low,  considering  the  wonder- 
ful possibilities  of  a  radio  receiving  set.  It  is  only  when 
one  desires  to  span  great  distances  and  to  have  the  dots 
and  dashes  or  the  radio-phone  music  amplified  so  as  to 
be  heard  throughout  a  room,  without  the  use  of  the  usual 
telephone  head  set,  that  the  cost  mounts  up.  Even  so,  the 
cost  is  still  no  greater  than  that  of  a  good  phonograph,  and 
certainly  less  than  half  the  cost  of  a  low-priced  automo- 
bile. After  all,  it  is  a  question  of  what  is  expected  of 
the  receiving  equipment,  and  successful  results  demand 
that  the  receiving  equipment 'be  fitted  to  the  requirements. 

Essentials  of  Radio  Reception 

No  matter  how  simple  a  receiving  set  may  be  and  how 
modest  the  requirements,  there  are  certain  essentials  which 
must  be  provided.     Thus  we  have : 

First — ^One  or  more  wires  elevated  from  the  ground 
and  properly  Insulated,  to  form  the  antenna  or  the  aerial. 
The  purpose  of  the  antenna,  or  aerial,  is  to  intercept  the 
radio  waves  and  to  convey  them  to  the  receiving  apparatus. 


94  RADIO  FOR  EVERYBODY 

An  alternative  to  the  aerial  is  the  loop,  which  is  simply 
a  large  frame  with  several  turns  of  wire,  which  may  be 
used  indoors  with  fair  results. 

Second — A  good  connection  with  the  ground,  which 
may  take  the  form  of  a  connection  with  a  gas,  water,  or 
steam  pipe.  In  the  absence  of  any  one  of  these  pipes,  such 
as  in  remote  country  districts,  a  good  ground  may  be  ob- 
tained in  other  ways,  as  described  further  on.  Again, 
the  ground  may  take  the  form  of  an  insulated  network 
of  wires,  placed  below  the  aerial  but  elevated  from  the 
ground  by  a  few  feet.  Such  a  ground  is  known  as  a 
counterpoise,  and  is  frequently  used.  No  ground  is  re- 
quired when  a  loop  is  employed  instead  of  an  aerial. 

Third — A  means  of  altering  the  wave  length  of  the 
aerial  circuit  and  the  receiving  apparatus,  so  as  to  inter- 
cept and  detect  any  desired  radio  waves  to  the  more  or 
less  complete  exclusion  of  undesired  waves.  Tuning  is 
accomplished  by  a  wide  variety  of  instruments  and  meth- 
ods, as  will  be  explained. 

Fourth — A  means  of  changing  the  frequency  of  the 
incoming  waves  from  radio  frequency  to  audio  frequency 
so  that  they  may  be  heard.  The  instrument  that  accom- 
plishes this  result  is  known  as  the  detector,  and  is  of 
the  crystal  type  or  the  vacuum  tube  type. 

Fifth — A  companion  instrument  to  the  detector,  which 
takes  the  audio  frequency  current  delivered  by  the  detec- 
tor, after  the  latter  has  converted  the  radio  frequency 
into  audio  frequency  current,  and  makes  it  audible  to 
the  human  ear.  This  instrument  may  be  any  form  of 
telephone  receiver,  ranging  from  the  single  receiver  to 
the  head  set  and  to  the  loud-speaker. 

The  first  step,  then,  is  to  consider  the  aerial  or  an- 
tenna for  receiving  purposes.  While  the  same  aerial  or 
antenna  may  be  used  for  both  receiving  and  transmitting 
purposes,  as  a  general  thing  these  purposes  are  by  no 
means  interchangeable  if  really  efficient  results  are  de- 
sired. Thus  the  ideal  antenna  for  receiving — antenna, 
by  the  way,  is  a  happier  term  for  the  receiving  end  than 
aerial,  the  latter  applying  more  particularly  to  transmis- 


RADIO  FOR  EVERYBODY  95 

sion  work — is  a  single  'wire,  insulated  at  both  ends,  ele- 
vated some  20  or  more  feet  from  the  ground  and  mea- 
suring 150  feet  in  length.  A  shorter  wire  makes  for  a 
lower  efficiency,  while  a  longer  wire,  strange  as  it  may 
seem,  also  detracts  from  the  receiving  efficiency.  The 
reason  for  this  is  that  the  wave  length  of  the  aerial 
should  be  as  nearly  as  possible  that  of  the  radio  waves  to 
be  intercepted.  Otherwise,  in  the  case  of  a  shorter  wire, 
it  is  necessary  to  add  inductance  in  order  to  bring  up  the 
wave  length,  and  such  inductance  means  some  loss  of 
energy.  Furthermore,  a  shorter  wire  v^ill  not  intercept 
as  much  of  the  radio  waves  as  a  longer  one.  Now,  on  the 
other  hand,  a  longer  wire  intercepts  more  of  the  radio 


How  a  receiving  antenna  may  be  installed  in  the  country.     The 

single  wire  may  be  run  from  the  house  to  a  barn,  tree,  clothes 

pole  or  other  support. 

wave,  but  it  is  necessary  to  use  either  a  variable  or  fixed 
condenser  in  series  with  the  antenna  in  order  to  bring 
down  the  wave  length,  and  such  practice  means  a  loss  of 
energy.  O'f  course,  we  are  considering  the  receiving  set 
on  the  basis  of  amateur  and  radio-phone  reception.  If  one 
desires  to  receive  the  long-wave  commercial  stations,  a 
longer  wire  is  quite  satisfactory.  Indeed,  for  the  best 
kind  of  work  it  may  be  well  to  have  several  antennae, 
arranged  for  various  classes  of  service. 

The  Aerial  and  the  Ground  for  Receiving 

As  for  the  kind  of  wire  to  use,  there  is  considerable 
latitude;  indeed,  in  this  general  subject  of  antennae  for 
receiving  purposes   there   are   no   fixed   rules   to   go  by. 


96  RADIO  FOR  EVERYBODY 

Various  kinds  of  wire  are  used,  among  these  being  plain 
aluminum  wire,  which  has  the  advantage  of  being  exceed- 
ingly light  and  quite  low  in  cost ;  plain  copper  wire,  which, 
of  course,  is  an  excellent  conductor,  although  somewhat 
costly,  especially  in  the  larger  sizes ;  hard-drawn  copper 
\vire,  which  has  all  the  advantages  of  plain  copper,  plus 
greater  strength ;  copper-clad  steel  wire,  which  has  great 
strength  coupled  with  good  conductivity;  stranded  phos- 
phor-bronze wire,  which  has  long  been  the  standard  aerial 
wire  in  commercial  and  Government  work ;  and  annunci- 
ator or  bell  wire,  which  is  insulated.    The  last-mentioned 


Materials  with  which  to  erect  the  antenna,  compris- 
ing a  coil  of  bare  copper  or  copper-clad  steel  wire, 
insulators,  ground  clamp,  insulated  wire  for  lead-in, 
porcelain  tube  to  insulate  lead-in  passing  into  build- 
ing, and  a  lightning  arrester. 

wire  may  sound  freakish  and  merely  an  improvision ;  but 
as  a  matter  of  fact  the  insulation  makes  little  difference. 
Why?  Simply  because  if  the  insulation  were  not  there, 
the  space  immediately  surrounding  the  copper  wire  would 
be  taken  up  by  air,  and  the  air  is  about  as  much  of  an 
insulator  as  the  usual  cotton  and  paraffin  insulation. 
Hence  it  makes  little  difference  one  way  or  the  other,  and 
annunciator  or  bell  wire  recommends  itself  in  many  in- 
stances because  it  is  so  easy  to  obtain.  A  pound  of  No. 
18  wire  is  sufficient  for  a  good  single-wire  antenna. 

Aluminum  wire  is  not  recommended  very  enthusiastic- 
ally by  the  author.     Back  in  the  early  days  of  amateur 


RADIO  FOR  EVERYBODY  97 

radio,  when  we  used  to  spend  our  hard-earned  money  by 
the  cent  rather  than  by  the  dollar,  aluminum  wire  was 
widely  employed  because  a  good  many  feet  of  it  came 
with  each  pound.  However,  it  has  not  the  conductivity 
of  copper  by  a  good  margin,  and  even  when  using  No. 
14:  size  it  is  not  as  good  as  No.  18  copper.  Furthermore, 
it  is  difficult  to  solder  aluminum  wire  joints,  yet  they 
should  be  soldered.  If  the  joints  are  not  soldered,  water 
gets  into  them  and  oxidizes  the  aluminum  wire.  The 
oxide  takes  the  form  of  a  white  crust,  and  is  of  such 
high  resistance  that  it  reduces  the  efficiency  of  the  antenna 
materially.  Hence  aluminum  v^ire  should  not  be  used  ex- 
cept where  cost  is  a  prime  essential,  and  even  so,  a  small 
sized  copper  wire  is  preferable. 

Copper-clad  steel  wire  is  almost  as  good  as  solid  copper, 
and  costs  considerably  less.  It  is  the  kind  of  wire  that 
is  supplied  with  the  usual  antenna  equipment  as  sold  by 
wireless  dealers.  Hard-drawn  copper  wire  of  No.  12  or 
Xo.  14  guage  is  satisfactory  for  antenna  construction ; 
however,  stranded  silcon  bronze  or  phosphor  bronze  wire 
is  more  durable  and  w^ll  stand  greater  strains. 

Now  then,  having  selected  the  wire,  the  next  step  is 
to  erect  the  antenna.  Sup^rts  are  sought,  since  for  re- 
ceiving purposes  the  height  of  the  antenna  is  not  so  im- 
portant and  the  antenna  may  be  supported  by  any  suitable 
object,  such  as  a  house,  tree,  flag-pole,  clothes-pole,  and 
so  on,  making  masts  or  supporting  towers  unnecessary. 
If  possible,  the  wire  should  be  horizontal,  which  means 
that  the  supports  at  both  ends  must  be  of  the  same  height. 

It  is  necessary  to  insulate  the  antenna  wire.  This  is 
done  by  placing  little  porcelain  knobs  or  porcelain  cleats, 
such  as  are  used  in  exposed  electric  light  wiring,  at  each 
end  of  the  wire,  as  shown  in  the  accompanying  sketch. 
Such  improvised  insulators  will  serve  quite  nicely  for 
ordinary  installations,  but  if  the  antenna  is  apt  to  be  sub- 
jected to  considerable  strains  from  high  winds  as  well 
as  coatings  of  ice,  it  may  be  well  to  substitute  regular 
antenna  insulators.  These  take  the  form  of  special 
moulded  electrose  insulators,  with  heavy  galvanized  rings 


98 


RADIO  FOR  EVERYBODY 


Screw  Eye 
No.  14  Copper     ^ 
Tie  Wire 


No.  14  Copper 
Antenna  Wire 


Insulator 


Simple    way    to    insulate    and    fasten    the    farther    end    or    free 
end  of  a   sing:le  wire  antenna. 

moulded  right  into  the  brown  insulating  material.  The 
insulator  proper  is  provided  with  many  deep  grooves,  so 
as  to  lengthen  the  surface  of  the  insulator  and  therefore 
increase  its  resistance  to  leakage  or  loss.  Small  electrose 
insulators  will  do  for  the  receiving  station,  if  placed  at 
the  ends  of  each  antenna  wire,  between  the  wire  and  the 
support. 

Another  popular  form  of  antenna  insulator  is  one  made 


No.  14  Copper 
Antenna  Wire 


No.  14  Copper 
Tie  Wire 


Insulator 

No.  14  Insulated  ,^^^/ 
Copper  Wire 


How  the  nearer  end  or  lead-in  end  of  the  antenna  is  fastened 

and   insu-lated.      The   lead-in   w^ire  is   fastened    to   the   antenna 

wire  by  means   of  a  connector,  or  is   soldered   so  as  to  insure 

a  perfect   and  lasting  joint. 


RADIO  FOR  EVERYBODY  99 

of  micarta,  with  a  metal  lined  hole  at  each  end.  This 
kind  of  insulator  is  supplied  with  an  antenna  equipment 
now  on  the  market,  and  has  the  advantage  of  considerable 
mechanical  strength  with  good  insulating  properties. 

In  the  country  the  erection  of  the  antenna  is  a  simple 
matter,  for  there  are  virtually  no  restrictions  such  as  one 
encounters  in  the  crowded  city.  Thus  the  antenna  wire 
may  be  run  from  the  roof  of  the  house  to  the  roof  of 
the  barn,  or  even  from  the  second  floor  of  the  house  to 
the  roof  of  the  barn.  If  no  barn  is  available,  then  the 
farther  end  of  the  wire  may  be  supported  by  a  clothes- 
pole  or  tali  tree. 

The  author,  while  this  book  is  being  written,  is  using  a 
small  antenna  consisting  of  a  single  wire  about  60  feet 
long,  running  from  the  third  floor  of  a  frame  house  to  a 
tree  in  the  yard.  The  antenna,  made  of  No.  18  annun- 
ciator or  bell  wire,  is  about  40  feet  high  at  one  end,  and 
certainly  not  over  10  feet  at  the  farther  end.  While  this 
antenna  is  an  improvised  one  and  is  to  'be  replaced  by 
a  single  length  of  hard-drawn  copper  wire,  some  150  feet 
long,  running  from  the  house  to  a  taller  tree  than  the 
present  one,  it  has  proved  quite  satisfactory  for  receiving 
the  radio-phone  service  from  the  Newark  station,  about 
45  miles  distant,  and  the  radio-phone  service  from  the 
Pittsburgh  station,  considerably  more  than  400  miles  dis- 
tant. However,  the  less  efficient  the  antenna  happens  to 
be,  the  better  must  be  the  receiving  equipment.  The  Pitts- 
burgh station  ordinarily  is  received  by  the  author  with 
one  stage  of  amplification,  and  when  the  atmospheric  con- 
ditions are  unfavorable,  two  stages  of  amplification  must 
be  employed.  The  Newark  station  is  generally  heard  with 
the  vacuum  tube  detector  alone,  although  one  stage  of 
amplification  makes  it  more  enjoyable. 

In  the  city,  the  antenna  presents  a  problem.  What  with 
congested  conditions  and  a  none  too  obliging  landlord, 
the  radio  enthusiast  is  often  forced  to  resort  to  a  little 
strategy.  The  author,  only  recently  a  resident  of  the 
suburbs,  traveled  a  rather  thorny  path  in  pursuit  of  radio 
while   residing  in  New  York  City.     One  antenna   after 


100 


RADIO  FOR  EVERYBODY 


another  was  removed  by  a  highly  miHtant  janitor,  carrying 
out  the  instructions  of  an  overbearing  landlord.  The 
antennae  took  all  kinds  of  forms,  ranging  from  single  wires 


,«N5ULATOR 


INSUUATOR> 


SIMPLE    SINGLE-WIRE 


L-TYPE 


How    the    L.-type    single    wire   antenna   is    installed.      Such    an- 
tennae should  not  be  shorter  than  60  feet  and  not  longer  than 
150  feet  for  best   results  in  the  reception  of  short  waves   such 
as  are  used  in  amateur  and  radio-phone  work. 


running  from  one  house  to  another  across  a  court  or  large 
open  space,  to  a  number  of  wires  supported  on  poles  or 
supported  by  the  dumbwaiter  houses  on  the  roof.  Finally, 
the  author  simply  ran  a  single  wire  down  a  chimney,  from 
the  roof  to  the  cellar,  a  distance  of  about  75  feet.  This 
wire  was  never  detected,  and  it  was  tapped  in  the  kitchen 
of  the  apartment,  through  a  flue  that  led  into  the  chimney. 
A  poor  antenna  at  best,  it  served  to  receive  the  Newark 
radio-phone  service  some  15  miles  distant. 

All  sorts  of  improvisions  may  be  resorted  to  when  an 
outdoor  antenna  is  not  practical.     A  metal  bedstead,  the 


T-TYPE    ANTENNA,      TAPPED     IN    CENTER 

Arrangement    of    a    T-type    single    wire    antenna.       When    the 

antenna  runs  longer  than  150  feet,  it  may  be  desirable  to  tap 

it  in   the  center   for  the   lead-in,    provided    the   lead-in   can   be 

dropped   straight    down  to   the   receiving   apparatus. 

telephone  line  with  a  fixed  condenser  in  series,  the  bell 
wiring  of  the  house,  the  fire-escapes,  an  indoor  antenna 
of  any  shape  and  size — all  these  improvisions  are  possible 
for  nearby  signals. 


RADIO  FOR  EVERYBODY 


101 


So  far,  only  single  wire  antenna  have  been  dealt  with. 
The  wire  is  tapped  at  one  end  by  another  length  of  wire 
leading  to  the  receiving  instruments.  This  second  wire  is 
called  the  lead-in,  and  it  is  preferable  to  have  it  of  insulated 
wire,  so  that  if  it  touches  a  wall  or  roof  coping  or  other 
object  there  will  not  be  the  leakage  that  would  occur  with 
bare  wire. 

But  supposing  the  antenna  is  stretched  over  a  greater 
distance  than  say  125  or  150  feet,  and  the  receiving  station 
must  be  located  near  the  middle  of  the  span,  then  what? 
Simple  enough.  The  antennae  so  far  described  are  called 
the  L-type,  because  the  antenna  proper  and  the  lead-in 
form  an  inverted  L  shape.     If  the  antenna  is  to  be  200  or 


INSULATORS 


V-TYPE    ANTENNA 

The  V-type   antenna,   consisting    of   two   wires    of   about    equal 
length,  diverging  to  two   different  supports. 

300  feet  long,  then  the  tap  is  taken  at  the  center,  and  to  all 
intents  and  purposes  the  antenna  is  equivalent  to  two 
single  wires  100  or  150  feet  long.  In  other  words,  the 
wave-length  of  the  long  wire  is  halved  by  tapping  it  at 
the  center.  This  type  of  antenna  is  known  as  the  T-type. 
Another  modification  of  this  type  is  the  V-type,  in  which 
two  wires  of  about  the  same  length  run  from  the  lead-in, 
at  one  end,  divergingly  to  two  more  or  less  separated  sup- 
ports at  the  farther  end.  This  form  of  antenna  has  the 
same  wave-length  as  the  average  of  the  two  wires,  and  is 
more  efficient  than  a  single  wire. 

Then  there  is  the  umbrella  type  which  must  be  employed 
where  a  stretch  of  over  40  feet  is  not  to  be  had.  In  this 
case  a  tall  pole  must  be  used  as  the  center  support,  and 
the  wires  numbering  six  to  ten,  radiate  downward  in  all 


103 


RADIO  FOR  EVERYBODY 


directions,  being  insulated  at  the  top  and  bottom  ends. 
The  lower  end  of  each  wire  should  be  20  feet  from  the 
base  of  the  pole,  so  as  to  obtain  as  much  spread  as  possible. 
The  lead-in  wire  is  taken  from  the  top,  the  various  wires 
being  connected  together  and  spliced  to  the  lead-in  wire. 
The  erection  of  the  umbrella  type  is  somewhat  complicated, 
as  compared  with  the  simple  single  wire  antennae,  and  is 
therefore  not  recommended  for  receiving  purposes  except 
in  cases  of  absolute  necessity. 

For  receiving  purposes,  a  multi-wire  L-type  or  T-type 
antenna  is  not  necessary,  hence  a  description  of  the  multi- 
wire  antenna  e — or  more 
properly  called  aerials,  since 
they  are  to  be  used  for  trans- 
mitting— will  be  left  for  the 
chapter  dealing  with  trans- 
mission. 

The  lead-in  connects  the 
antenna  with  the  receiving 
instruments.  One  of  the 
problems  is  to  bring  the  an- 
tenna through  the  wall  or 
window  into  the  station,  no 
matter  where  it  may  be  lo- 
cated. Some  amateurs  pre- 
fer to  bore  a  hole  through  the  glass  pane  of  a  window,  but 
this  is  a  somewhat  tedious  job  and  one  that  is  apt  to  end 
in  a  disaster  unless  there  is  considerable  skill  behind  it.  A 
better  plan  is  to  cut  a  board  in  order  that  it  will  fit  in  the 
window  frame  below  the  partly  raised  window,  so  as  to 
keep  out  the  air.  The  window  is  brought  down  on  the 
board.  A  hole  is  made  in  the  board  and  provided  with  a 
porcelain  tube  insulator,  through  which  is  passed  the  lead- 
in.  The  lightning  switch  or  arrester  can  be  mounted  on 
the  board,  if  desired. 

Then  there  is  the  ground  connection,  which  is  highly 
important.  Indeed,  the  effectiveness  of  the  antenna  system 
depends  largely  upon  the  character  of  the  ground  connec- 
tion.    The  most  practical  ground  connection  is  the  water 


UMBRELLA     TYPE     ANTENNA, 

The  umorella  type  antenna, 
which  is  only  employed  when 
it  is  impossible  to  obtain  a 
sufficient  span  for  the  antenna. 
This  type  is  quite  popular  in 
transmission  work. 


RADIO  FOR  EVERYBODY 


103 


supply  system.  Where  this  is  not  available,  pipes  con- 
nected with  the  heating  or  gas  system  may  be  used,  al- 
though these  are  to  be  regarded  with  some  suspicion. 
Sometimes  a  non-conducting  length  of  pipe  is  inserted  in 
the  gas  line  before  it  reaches  the  earth,  so  that  it  is  not  a 
true  "ground"  connection.  However,  the  results  obtained 
soon  disclose  whether  the  pipe  is  grounded  or  not. 

At  any  rate,  the  pipe  selected  is  scraped  with  a  knife 


A  convenient  manner  in  which  to  bring  the  lead-in  wire 
into  the  house.  A  board  of  about  the  same  width  as  the 
window  frame  is  inserted  at  the  bottom  or  top  of  the  win- 
dow frame,  and  the  window  is  then  pushed  against  it  so  as 
to  shut  out  the  air  in  cold  weather.  The  lead-in  passes 
through  a  hole  in  the  board,  which  may  be  insulated.  Thus 
the  window^  can  be  raised  or  lowered  without  trouble. 


or  rubbed  clean  with  sandpaper  until  it  is  bright,  and 
connection  is  made  by  means  of  ground  damps,  which 
can  be  obtained  at  any  electrical  supply  store,  or  by  wrap- 
ping ten  or  more  turns  of  copper  wire  about  the  cleaned 
section  of  the  pipe,  good  and  tightly  so  as  to  make  firm 
contact.  No.  14  wire  is  preferable  for  the  ground  lead, 
althoug^h  anything  up  to  No.  20  will  do.  Naturally,  the 
insulation  is  removed  from  the  wire  at  the  point  where  it 
makes  contact  with  the  pipe.     If  possible,  the  wire  should 


104  RADIO  FOR  EVERYBODY 

be  soldered,  for  one  cannot  take  too  much  pains  with  the 
ground  connection.  More  receiving  troubles  originate 
with  a  poor  ground  connection  than  from  any  other 
source,  for  the  good  and  sufficient  reason  that  this  end 
of  the  installation  seems  so  simple  that  it  is  often  slighted. 
Too  much  is  taken  for  granted.  However,  if  no  solder  is 
used,  then  it  is  well  to  wind  insulating  or  friction  tape 
about  the  connection,  so  as  to  hold  it  firmly  in  position 
and  to  prevent  corrosion  between  the  copper  wire  and 
the  pipe. 

Where  the  above-mentioned  means  of  ground  connec- 
tion are  not  available,  wires  or  plates  may  be  buried  in 
the  earth  and  connected  to  the  apparatus.  Such  wires  or 
plates  should  include  an  area  of  at  least  30  square  feet, 
buried  in  damp  soil.  Another  method  is  to  attach  the 
ground  wire  to  a  metal  bucket  which  is  then  lowered  into 
a  well,  a  brook,  a  pond  or  a  lake. 

Doing   Away   with   the   Ground   Connection — The 
Counterpoise 

There  are  places  where  a  ground  connection  is  out  of 
the  question.  Take,  for  instance,  desert  country,  where 
the  soil  is  sandy  and  without  moisture  of  any  kind.  Or 
again,  take  rocky  country,  where  there  is  just  a  thin  layer 
of  soil  over  solid  rock.  Obviously,  a  ground  is  out  of  the 
question.  It  then  becomes  necessary  to  resort  to  what  is 
known  as  the  counterpoise,  which  consists  of  at  least  the 
same  number  of  wires  as  the  antenna,  suspended  beneath 
the  antenna  and  used  in  place  of  the  usual  ground  connec- 
tion. The  counterpoise  wires  should  be  elevated  but  a 
few  feet  from  the  ground,  and  just  as  carefully  insulated 
as  the  antenna  wires. 

In  aircraft,  the  counterpoise  form  of  ground  is  em- 
ployed. It  must  be  evident  that  no  ground  connection  is 
possible  w^hen  the  machine  is  in  flight.  So  the  antenna 
consists  of  one  or  more  wires  which  are  paid  out  while 
the  machine  is  in  flight,  and  which  trail  behind  some  100 
or  more  feet  in  length,  while  the  ground  is  represented 


RADIO  FOR  EVERYBODY 


105 


by  a  counterpoise  made  up  of  all  the  metal  fittings  and 
stay  wires  and  control  cables  of  the  machine. 

The  counterpoise  is  especially  efficient  and  almost  neces- 
sary in  conjunction  with  continuous  wave  transmission,  as 
will  be  described  farther  on  when  we  come  to  transmitting 
equipment. 

When  the  summer  comes  along  in  such  locaHties  where 
thunder  storms  are  common  occurrences,  it  is  necessary 
to   give   some  consideration   to  lightning.     The   antenna, 


How  the  lightning:  switch  is  installed.  It  should  always  be 
installed  on  the  outside  of  the  building,  with  the  ground  wire 
going  as  straight  as  possible.  The  blade  of  the  switch  is  con- 
nected with  the  antenna,  one  jaw^  is  connected  w^ith  the  receiving 
set,  and  the  other  is  connected  directly  to  the  ground.  Thus 
the  antenna  may  be  connected  with  the  receiving  set  or 
"grounded." 


after  all,  presents  but  a  small  target  to  lightning,  but  even 
so  it  is  well  not  to  take  chances.  Just  as  'electric  power 
lines  and  telephone  and  telegraph  lines  must  be  protected 
against  lightning,  so  must  the  antenna  be  provided  with 
some  protective  device.  The  Fire  Underwriters  require 
the  installation  of  a  lightning  switch  or  protective  device, 


106  RADIO  FOR  EVERYBODY 

and  this  should  be  done  as  a  precautionary  measure.  The 
approved  type  of  Hghtning  switch  is  a  single-pole,  double- 
throw,  600-volt,  100  ampere,  knife  switch,  mounted  on  a 
composition  base.  The  slate  base  so  often  provided  with 
such  switches  is  not  satisfactory,  because  -it  absorbs 
moisture  and  causes  quite  a  little  leakage  of  the  radio 
currents  when  used  in  this  manner.  Lightning  switches 
are  required  to  be  mounted  on  the  outside  of  the  building, 
and  the  ground  connection  may  be  made  to  an  iron  pipe 
driven  several  feet  into  the  ground.  This  connection 
should  ibe  made  with  weatherproof  copper  wire.  No.  6 
B.  &  S.  guage  or  larger.  It  may  well  be  worth  while  for 
the  radio  enthusiast  to  mount  the  switch  on  electrose  pil- 
lars, since  these  oflfer  the  maximum  insulation,  and  the 
pillars,  in  turn,  can  be  mounted  on  a  stout  oak  board. 

However,  where  only  receiving  apparatus  is  being  used 
— and  we  are  dealing  with  receiving  apparatus  only  in  this 
chapter — lightning  protection  may  be  obtained  by  the  use 
of  a  vacuum-gap  protective  device.  This  device  should 
be  installed  in  place  of  the  lightning  switch  and  should  be 
permanently  connected  to  both  the  antenna  and  ground 
wires.  The  vacuum-gap  lightning  protector  is  made  in 
several  different  types  both  for  indoor  and  outdoor  in- 
stallation. The  outdoor  type  is  preferable,  because  the 
shortest  possible  route  to  the  ground  should  be  provided 
for  any  possible  lightning  charge.  All  radio  supply 
houses  handle  the  various  types  of  vacuum-gap  lightning 
protector. 

Using  the  Loop  in  Place  of  Antenna  and  Ground 

Interesting  results  may  be  obtained  by  using  a  loop  in 
place  of  the  usual  antenna  and  ground,  although  it  is  well 
to  remember  that  the  loop  is  by  no  means  as  effective  as 
an  outdoor  antenna.  A  loop  consists  of  a  suitable  wooden 
frame  on  which  are  wound  a  number  of  turns  of  bare  or 
insulated  wire.  The  frame  should  be  suspended  or  mounted 
in  such  a  manner  as  to  permit  of  being  swung  in  all  direc- 
tions. The  loop  receives  best  when  it  is  pointing  edge  on 
towards  the  transmitter,  and  it  is  this  characteristic  of  the 


RADIO  FOR  EVERYBODY 


107 


loop  which  makes  it  interesting.  It  indicates  the  direction 
of  the  transmitter  being  intercepted,  and  this  forms  the 
basis  of  the  radio  compass  which  has  found  such  wide 
use  in  modern  navigation. 

Loops  are  of  two  general  types :  there  is  the  spiral  loop, 
which  is  of  the  flat  type,  inasmuch  as  all  turns  are  in  the 


A    solenoidal   type    loop    of    simple    construction, 
which  can  be  used  in  place  of  the  usual  antenna. 


same  vertical  plane  and  each  turn  encloses  an  area  smaller 
than  the  preceding  turn ;  and  there  is  the  solenoid  loop,  in 
which  the  coils  are  all  of  the  same  dimensions,  spreading 
out  horizontally  so  as  to  form  a  square  helix.  A  loop 
only  three  feet  in  diameter  is  sufficiently  large  to  pick  up 


108 


RADIO  FOR  EVERYBODY 


radio-phone  broadcasting  stations  a  few  miles  distant,  and 
larger  loops  may  be  employed  at  greater  distances.  Trans- 
atlantic reception  is  effected  by  means  of  loops,  which 
have  the  advantage  of  reducing  atmospheric  disturbances 
and  other  interference  to  a  minimum.     However,  loops 


The    spiral   or  flat   type    of   loop, 
which  may   be  readily  made  and 
which  affords  no  end  of  interest- 
ing possibilities. 

do  not  begin  to  prove  as  effective  as  outdoor  antennae, 
hence  amplifiers  must  be  resorted  to  when  using  loops. 
Since  the  number  of  turns  comprising  any  loop  depends 
largely  on  the  wave  length  desired  and  the  dimensions 
of  the  frame,  it  is  best  to  decide  the  exact  number  in  each 
case  by  experimentation.  To  this  end  the  loop  should 
be  made  with  bare  wire  so  that  one  can  tap  any  number  of 


RADIO  FOR  EVERYBODY  109 

turns,  or  the  insulated  wire  should  be  bared  at  certain 
points  so  as  to  permit  of  tapping.  More  will  be  said 
about  loops  in  the  chapter  on  operating  the  receiver. 


One  of  the  neatest  forms  of  loop.     The  turns  of  wire  are  spaced 
about  one   inch  apart  for  the  best  results. 

The  Irreducible  Minimum   Among  Receivers 

With  the  antenna  and  ground  accounted  for,  the  next 
step  is  to  consider  receiving  equipment.  The  simplest 
receiving  equipment  comprises  a  detector  and  a  single 
telephone  receiver.  The  detector,  as  we  have  already- 
learned,  is  a  device  which  changes  the  frequency  of  the 
incoming  waves  from  radio  frequency  to  audio  frequency 


no  RADIO  FOR  EVERYBODY 

so  that  they  may  be  heard  in  the  telephone  receiver.     Let 
us  consider  the  simplest  kind  of  detector. 

Nothing  could  be  less  complicated  or  less  expensive 
than  the  crystal  detector.  It  makes  use  of  one  of  several 
different  kinds  of  mineral  crystals  v^hich  possess  the  de- 
sirable characteristics.  The  most  popular  crystal  body 
today  is  galena  (lead  peroxide),  a  silvery  gray  mineral 
which  breaks  in  squares  with  mirror-like  surfaces.  Rest- 
ing on  the  galena  crystal  is  a  fine  piece  of  wire,  and  it  is 


GALENA    DETECTOR   WfTH   SPRING 
GALENA    AND    CRYSTAL  / 


CONTACT   DETECTOR 


SWITCH    FOR    EITHER 
ETECTOR 


A  crystal  detector  unit.     In  this  case  two  detectors  are  mounted 
on  the  sanie  base,  with  a  switch  for   selecting  either  detector. 

the  contact  between  the  crystal  and  the  wire  which  does 
the  rectifying  of  the  high  frequency  radio  energy,  of  the 
order  of  20,000  to  6,000,000  changes  of  direction  per  sec- 
ond, to  impulses  of  varying  strength  traveling  in  one 
direction  only,  and  therefore  capable  of  operating  a  tele- 
phone receiver.  Sometimes  another  crystal  is  employed  in 
contact  with  the  galena,  in  place  of  the  wire. 
-  Now  with  all  crystal  detectors  the  matter  of  adjustment 
is  an  important  one.  Unfortunately,  the  crystals  are  not 
uniformly  sensitive.  Here  and  there  on  a  given  surface 
there  are  sensitive  spots,  and  these  must  be  sought  out. 
Hence  when  using  a  crystal  detector  the  wire  member 
must  be  shifted  about  on  the  surface  of  the  galena  crystal 
until  a  sensitive  spot  is  found.  Once  a  sensitive  spot  is 
found,  the  detector  need  not  be  readjusted  for  some  time. 


RADIO  FOR  EVERYBODY  111 

However,  if  it  is  jarred  the  sensitive  contact  may  be  lost, 
and  readjustment  is  then  necessary. 

While  the  crystal  detector  is  far  more  sensitive  than  the 
earlier  forms  of  detector  employed  during  the  pioneer 
days  of  radio  communication,  it  is  not  nearly  as  efficient 
as  the  vacuum  tube  type,  v^hich  vv^ill  be  described  further 
on.  However,  the  crystal  type  is  inexpensive  and  may 
be  used  with  the  simplest  kind  of  equipment.  It  requires 
no  batteries  of  any  kind. 

The  simplest  receiving  set,  therefore,  consists  of  the 
antenna  and  ground  connected  to  a  plain  crystal  detector, 
with  a  telephone  receiver  in  parallel;  and  no  attempt  is 
made  to  tune  such  an  arrangement.  At  short  distances 
from  a  pow^erful  radio^phone  or  radio  telegraph  station,  a 
crude  receiving  set  of  this  kind  serves  quite  nicely. 
Indeed,  from  France  comes  the  little  receiving  set  v^hich 
may  be  carried  about  in  one's  pocket.  It  comprises  a 
telephone  receiver,  on  the  back  of  which  is  mounted  a 
crystal  detector.  Such  an  arrangement  is  used  in  Paris 
for  receiving  time  signals  from  the  powerful  Eiffel  tower, 
and  even  radio-phone  concerts  are  picked  up  at  consider- 
able distances  outside  the  French  metropolis,  when  using 
this  diminutive  receiver.  Instead  of  using  a  single  wire 
resting  on  the  galena  crystal,  this  device  has  ten  wires 
resting  on  ten  different  places  on  the  crystal,  and  a  switch 
is  provided  so  that  the  operator  can  select  any  one  of  the 
ten  wires.  Obviously,  one  or  more  of  the  wires  are  almost 
certain  to  be  resting  on  a  sensitive  spot ;  if  not,  the  crystal 
can  be  shifted  slightly,  so  as  to  give  ten  new  spots.  This 
idea  is  truly  ingenious,  and  works  out  very  well  in  prac- 
tice. The  little  set  is  provided  with  tiny  spools  containing 
the  necessary  connecting  cords  and  clips,  so  that  one  can 
hook  up  to  any  suitable  ground  and  to  anything  that  will 
act  as  an  antenna.  The  framework  of  a  large  awning, 
the  fire  escape,  an  iron  bedstead,  an  umbrella — all  these 
and  other  similar  metallic  objects  may  be  used  for  receiv- 
ing messages  from  powerful  stations  but  a  very  short 
distance  away. 


112 


RADIO  FOR  EVERYBODY 


Simplicity  Combined  with  Efficiency 

With  no  provision  made  for  tuning,  a  receiving  set  must 
perforce  be  of  a  low  order  of  efficiency.  Furthermore, 
all  signals  come  in  at  the  same  time,  if  several  transmitters 

are  working  in  the  immediate 
vicinity.  By  providing  the 
simplest  kind  of  tuning  device, 
the  efficiency  of  the  crystal  de- 
tector and  telephone  receiver  is 
immediately  improved. 

There  are  several  simple  types 
of  tuning  devices.  One  of  these 
is  the  inductance  coil,  which  con- 
sists of  a  large  number  of  turns 
of  copper  wire,  wound  in  a  single 
layer  on  a  solid  mandrel  or  tube, 
and  provided  with  some  means 
for  varying  the  number  of  turns 
of  wire  which  are  used.  A 
switch  may  be  employed,  with 
contact  points  so  arranged  as  to 
represent  say  every  ten  turns  of 
wire,  in  order  that  ten,  twenty, 
thirty,  forty  and  so  on  turns  may 
be  obtained  at  will.  Again,  two  switches  may  be  used, 
one  switch  working  by  groups  of  ten  or  twenty,  while  the 
other  switch  cuts  in  one  turn  at  a  time.  In  this  manner 
a  relatively  fine  adjustment  may  be  obtained.  If  68  turns 
represents  the  proper  adjustment,  the  first  switch  is  turned 
to  the  point  connecting  with  60  turns,  and  the  second 
switch  is  turned  to  the  eighth  turn  of  wire.  This  arrange- 
ment is  found  in  certain  of  the  present-day  receiving  sets. 
Another  means  of  varying  the  number  of  turns  of  an 
inductance  coil  is  a  sliding  contact,  which  moves  over  the 
bared  section  of  the  wire.  Such  a  device  is  termed  a 
tuning  coil,  and  is  illustrated  on  page  117.  Bare  or 
insulated  wire  may  be  used  on  the  tuning  coil,  so  long  as 
the  adjacent  turns  are  insulated  one  from  the  o'^tp^    -^^  ] 


ntri  G 


The  simplest  receiving  set 
that  will  give  fair  results, 
using  a  rough  tuning  coil, 
crystal  detector,  fixed  con- 
denser and  telephone. 


RADIO  FOR  EVERYBODY 


113 


the  proper  contact  is  afforded  between  slider  and  wire. 

There  are  several  ways  of  connecting  the  tuning  coiL 
a  typical  one  being  indicated  in  the  accompanying  diagram. 
It  will  be  noted  that  the  best  arrangement  calls  for  two 
sliding  contacts  or  "sliders"  as  they  are  termed,  and 
that  in  this  instance  the  detector  is 
really  in  a  separate  circuit  from  the 
antenna-ground  circuit.  It  will  be 
noted  that  this  two-circuit  arrange- 
ment is  by  far  the  most  efficient,  and 
in  the  most  advanced  types  of  receiv- 
ing equipment  the  two  circuits  are  even 
separated  from  each  other,  so  that 
there  is  no  physical  connection  between 
the  two.  A  small  fixed  condenser  is 
placed  across  the  telephone  receiver, 
as  indicated,  in  all  crystal  detector  cir- 
cuits of  this  general  category. 

The  tuning  coil,  with  its  sliding  con- 
tacts which  do  not  always  make  per- 
fect contact,  has  more  or  less  become 
obsolete.  In  its  place  we  now  find 
more  delicate  devices  which  give  a  finer 
adjustment,  since  the  continuous-wave 
transmitters  now  widely  employed  in 
radio  telephony  and  in  radio  telegraphy 
are  exceedingly  sharply  tuned  and  even 
a  fraction  of  a  turn  of  inductance  makes  a  considerable 
diff'erence.  So  present  practice  favors  another  form  of 
tuner  known  as  the  variometer. 

The  variometer,  which  is  shown  in  the  accompanying 
illustration,  comprises  a  fixed  set  of  coils  and  a  movable 
set  of  coils.  As  the  knob  of  the  variometer  is  turned,  the 
relationship  between  the  fixed  and  the  movable  coils  is 
altered.  When  the  variometer  dial  is  set  at  180,  or  what- 
ever may  be  the  maximum  dial  reading,  the  coils  are  so 
arranged  that  the  current  will  flow  in  the  same  direction 
in  each  set  of  coils,  thus  adding  wave  length  to  the  circuit 


Ti  e 


A  two-slide  tuning 
coil  arranged  for 
tuning  the  antenna- 
ground  circuit  and 
tlie  closed  detector 
circuit. 


114  RADIO  FOR  EVERYBODY 

in  which  the  variometer  is  placed.  When  the  dial  is  set 
at  0,  the  two  sets  of  coils  are  so  arranged  that  the  current 
will  he  flowing  in  opposite  directions  in  both  sets  of  coils, 
and  the  coils  are  then  said  to  be  in  opposition  or  ''bucking"' 
each  other.  In  that  condition  the  inductance  is  greatly 
reduced,  and  the  wave  length  is  therefore  at  a  minimum. 
Hence  a  considerable  range  of  wave-length  values  may 
be  obtained  with  very  fine  adjustment  by  the  turning  of 
the  variometer  knob.    There  are  no  loose  contacts  to  bother 


FIXED  COiL   OR    WINDING 


HANDLE    AND 
DIAL 


MOVABLE    CO!L   OR    WINDING 


The   mechanism   of  the   variometer.      This   instrument   consists   of 
two   sets  of  coils,  one  fixed  set  and  one  movable  set. 

with,  and  the  rotary  action  is  far  more  convenient  than 
the  movement  of  sliders  along  a  tuning  coil. 

In  the  inexpensive  receiving  sets  now  being  offered  to 
the  public,  the  tuning  is  effected  by  several  methods.  The 
lowest  priced  sets  use  merely  an  inductance  with  taps  taken 
off  at  regular  intervals  and  connected  to  the  points  of  a 


RADIO  FOR  EVERYBODY 


115 


switch.  This  rough  tuner  is  placed  across  the  detector  and 
telephone.  Since  the  telephone  offers  too  much  resistance 
10  the  passage  of  high-frequency  current  to  the  detector, 
a  small  fixed  condenser  is  placed  across  the  telephone. 
Such  a  set,  it  must  be  evident,  is  satisfactory  for  short 
distances  only,  and  cannot  tune  with  any  degree  of  ac- 
curacy so  as  to  throw  out  undesirable  stations  and  con- 
centrate on  any  given  station. 
The  sets  selHng  for  $20.00  or 
$25.00  are  of  a  better  grade, 
being  provided  with  either  a 
two-slide  tuning  coil^  with  the 
sliders  arranged  in  the  form 
of  swinging  arms  so  as  to  be 
operative  by  means  of  knobs, 
or  a  variometer.  A  crystal  de- 
tector is  supplied  with  such 
sets,  as  well  as  a  pair  of  tele- 
phone receivers.  A  finer  ad- 
justment m.ay  be  obtained  with 
such  arrangements  than  can 
possibly  be  obtained  v^ith  the 
simpler  sets,  and  of  course  the 
results  are  accordingly  ever  so 
much  better.  Sets  of  this  kind  may  receive  radio-phone 
service  over  a  distance  of  25  miles  or  less,  and  with  good 
conditions  obtaining  the  range  may  be  increased  to  50 
miles.  The  Newark  radio-phone  broadcasting  station  re- 
ceived word  some  time  ago  that  an  amateur  in  Albany 
some  120  miles  distant,  was  receiving  the  radio-phone 
music  with  a  crystal  detector,  and  this  case  is  perhaps 
not  so  unusual.  However,  freak  conditions  are  not  to 
be  depended  upon,  and  when  a  definite  distance  must  be 
spanned  day  after  day,  the  receiving  set  should  be  con- 
sidered on  the  basis  of  minimum  performance.  Radio 
telegraph  stations  carry  much  farther  than  radio-phone, 
so  that  these  same  sets  may  receive  radio  telegraph  sig- 
nals over  100  miles  distant. 


Wiring    scheme    for    a    single 
varioinet.er   and   a   crystal   de- 
tector.   This  arrangement  pro- 
duces  excellent   results. 


116  RADIO  FOR  EVERYBODY 

The  Mission  of  the  Variable  Condenser 

So  far,  we  have  only  dealt  with  inductance  as  a  means 
of  tuning.  Inductance  makes  for  greater  wave  length: 
the  more  inductance  is  placed  in  a  circuit,  the  greater  the 
wave  length.  There  is  another  device  for  varying  wave 
length,  and  that  is  capacity,  which  was  described  in  the 
first  chapter.    Capacity  is  presented  by  a  condenser,  which 


KNOB  ON  DIAL 


SHAFT  FOR 
MOVABLE  PLATES 


Outside  and  inside  views  of  a  variable  condenser,  showing  its 
simple    mechanism    for    varying    capacity. 

may  be  of  the  fixed  or  variable  kind.  For  the  present  we 
are  interested  in  the  variable  kind.  Various  forms  of 
variable  condenser  are  available,  some  with  fixed  and 
movable  plates,  the  movable  plate  being  hinged  so  that  it 
can  be  moved  toward  or  away  from  the  fixed  plate ;  others 
with  a  set  of  fixed  plates  and  a  set  of  movable  plates  that 
slide  in  grooves  and  pass  in  between  the  fixed  plates  with- 
out touching  them;  still  others  with  a  delicate  means  of 
increasing  or  decreasing  the  distance  between  a  fixed  and 
a  movable  plate ;  and,  finally,  the  rotary  type,  in  which 
there  is  a  set  of  fixed  plates  and  a  set  of  rotary  variable 
plates  which  glide  in  and  out  of   the  fixed, set  without 


RADIO  FOR  EVERYBODY  117 

touching  them.  The  maximum  capacity  is  secured  when 
the  plates  are  nearest  to  each  other  or  when  the  plates  are 
entirely  meshed,  as  the  case  may  be. 

There  is  a  simple  rule  that  applies  to  the  use  of  variable 
condensers  in  affecting  wave  length.  When  the  condenser 
is  in  series,  the  wave  length  is  reduced  considerably,  and 
hne  variations  may  be  obtained  by  adjusting  the  condenser. 
When  the  condenser  is  across  or  in  parallel  with  induc- 
tance, it  augments  the  wave 
length  in  proportion  to  the 
amount    of    capacity   use. 

The   value    of   the   variable 
condenser    comes    in    the    fine 
adjustment     of     which    it     is 
capable.     Thus  the  inductance 
typioai    two-slide  tmits  may  be  relatively  crude, 

tuning  coil.  yg^  the  variable  condenser  con- 

nected in  series  or  in  parallel  with  the  inductance  will 
serve  as  the  finishing  touch.  It  is  much  like  a  weighing 
operation,  in  which  weights  of  several  pounds  are  placed 
on  the  scale,  while  the  delicate  balancing  is  accomplished 
by  a  sliding  beam  weight.  It  is  for  this  reason  that  in 
many  radio  receiving  sets  the  inductance  is  varied  in  pretty 
big  steps,  while  the  finishing  off,  so  to  speak,  is  left  to  one 
or  more  variable  condensers  or  even  variometers,  since 
the  variometer  is  also  capable  of  fine  adjustment. 

The  crystal  detector  is  limited  to  short  distances  and 
to  weak  or  moderate  audibility  in  the  telephone  receivers. 
It  is  out  of  the  question  to  ask  for  a  loud-speaker  in 
connection  with  a  crystal  detector.  Again,  a  fairly  large 
aerial  must  be  used  in  connection  with  a  crystal  detector, 
unless  one  is  situated  within  five  to  ten  miles  of  a  radio- 
phone broadcasting  station,  or  within  thirty  miles  of  a 
radio  telegraph  station.  Hence,  sooner  or  later,  and  rather 
sooner  than  later,  the  radio  enthusiast  gets  around  to  the 
vacuum  tube  detector,  even  though  it  does  mean  storage 
batteries  and  dry  batteries,  as  well  as  more  elaborate  re- 
ceiving equipment.     But  the  results  are   so  much  more 


118  RADIO  FOR  EVERYBODY 

satisfactory  with  the  vacuum  tube  detector  that  there  is 
scarcely  any  comparison  between  such  a  set  and  the 
crystal  type. 

The  Vacuum  Tube  and  What  It  Does 

The  vacuum  tube  is  the  most  interesting  as  well  as  the 
most  useful  device  which  has  been  developed  during  the 
progress  of  the  radio  art.  Without  going  into  the  history 
of  this  device,  it  may  be  said  that  Edison  originally  discov- 
ered the  peculiar  behavior  of  an  incandescent  lamp  fila- 
ment by  inserting  an  extra  wire  in  a  lamp  bulb.  He 
discovered  the  fact  that  when  a  lamp  filament  is  cold,  no 
current  can  be  passed  across  the  vacuum  between  the 
filament  and  the  extra  wire  or  plate  inserted  in  the  vacuum. 
However,  the  moment  the  filament  is  brought  up  to  incan- 
descence, a  current  can  be  passed  across  the  vacuum  gap 
between  the  filament  and  the  plate ;  but  the  current  can 
only  be  passed  in  one  direction,  since  this  device  is  a  uni- 
directional or  uni-lateral  conductor  of  electricity.  Thus 
the  vacuum  tube,  as  this  device  is  called,  may  be  used  to 
rectify  alternating  current,  since  it  allows  the  current  to 
flow  in  one  direction  only  and  therefore  converts  alter- 
nating current  into  pulsating  direct  current.  This  prin- 
ciple is  employed  in  certain  storage  battery  recharging 
outfits,  as  well  as  in  the  detection  of  radio  signals. 

What  really  takes  place  in  the  vacuum  tube  is  subject 
to  a  good  deal  of  theorizing,  and  bulky  volumes  have  been 
prepared  on  the  subject.  It  is  not  within  the  province  of 
this  book  to  deal  with  theories,  but  suffice  it  to  state  that 
the  white  hot  filament  gives  off  milHons  of  infinitesimal 
electrically  charged  units  known  as  electrons.  These 
electrons  travel  from  the  filament  to  the  relatively  cool 
wire  or  plate  placed  in  the  vacuum  tube,  and  thus  form  a 
bridge  over  which  one-way  traffic  of  outside  electric  cur- 
rent is  permitted.  Depending  on  the  number  of  electrons, 
the  bridge  is  of  greater  or  less  capacity,  and  therefore 
accommodates  more  or  less  traffic. 

Now  in  the  present-day  vacuum  tube  there  is  a  traffic 


n-     ^ 

X)  0 

,"0  z 

!jR 

2H 

> 

2> 

C/) 

o  r> 

m 

on  H 

120  RADIO  FOR  EVERYBODY 

officer,  so  to  speak,  who  decides  how  much  traffic  shall 
pass  over  the  electronic  bridge.  It  was  Dr.  Lee  de  Forest, 
the  radio  pioneer  and  inventor,  who  discovered  how  the 
traffic  could  be  regulated,  and  introduced  what  we  are 
pleased  to  call  a  traffic  officer  for  the  purpose  of  an  ana- 
logous explanation.  This  third  member,  known  as  the 
grid,  surrounds  the  filament  and  comes  between  it  and 
the  plate,  so  that  the  electrons  must  pass  through  the 
grid  in  order  to  reach  the  plate.  Any  charge  which  is 
impressed  on  the  grid  immediately  affects  the  electronic 
flow,  allowing  a  greater  or  less  flow ;  and,  consequently, 
the  external  current  being  passed  over  the  electronic 
bridge,  between  the  filament  and  the  plate,  is  likewise 
altered  by  the  grid  charge — our  little  traffic  officer,  as 
it  were.  The  grid  consists  of  a  piece  of  wire  bent  in  zig 
zag  form  or  again  as  a  perfect  helix  or  flattened  helix, 
surrounding  the  filament  and  separating  the  latter  from 
the  plate. 

The  vacuum  tube  is  a  most  sensitive  device.  The  slight- 
est charge  impressed  on  the  grid  controls  faithfully  and 
instantly  a  rather  strong  current  flowing  between  filament 
and  plate.  In  this  manner  it  becomes  possible  to  control 
a  strong  current  by  means  of  a  weak  current.  The  incom- 
ing radio  waves  are  led  to  the  grid,  where  they  serve  to 
control  the  electronic  flow,  and  this  in  turn  controls  the 
flow  of  current  through  the  tube  to  the  telephone  receiv- 
ers. The  arrangement  is  such  that  the  radio  waves  are 
converted  into  audible  sounds  in  the  telephone  receivers — 
loud,  clear  signals,  such  as  never  could  be  obtained  with  a 
crystal  detector. 

The  vacuum  tube  can  be  used  for  a  great  many  differ- 
ent things.  It  is  a  rectifier  of  alternating  current ;  that  is, 
it  converts  alternating  current  of  almost  any  frequency 
and  of  any  strength  within  its  capacity  into  direct  current. 
It  can,  conversely,  convert  direct  current  into  alternating 
current  of  a  wide  range  of  frequencies.  It  permits  of 
controlling  a  powerful  current  with  a  weak  current;  this 
feature  is  the  basis  of  the  amplifier,  since  the  character  - 


RADIO  FOR  EVERYBODY  121 

istics  of  a  weak  current  are  impressed  on  a  current  several 
times  as  powerful,  therefore  giving  that  much  louder 
response  in  a  telephone  receiver.  This  characteristic  is 
also  the  basis  of  the  telephone  repeaters,  now  employed 
in  long-distance  telephony.  Vacuum  tubes  permit  of  re- 
building attenuated  telephone  currents  at  any  desired  in- 
terval of  line,  so  that  a  greater  distance  may  be  spanned. 
The  vacuum  tube,  of  various  capacities  ranging  from  the 
small  5-watt  tube  to  the  large  250-watt  tubes,  can  also  be 
used  for  transmitting  purposes,  but  that  is  another  story 
which  is  left  for  later  on. 

The  "A"  Battery  and  the  ''B"  Battery  of  Vacuum 

Tubes 

Now  the  use  of  any  vacuum  tube  involves  a  battery  for 
heating  the  filament,  which  is  the  "A"  battery  but  is  more 
commonly  referred  to  as  the  filament  battery,  as  well  as  a 
high-voltage  or  '*B"  battery  which  serves  to  pass  current 
across  the  electronic  bridge  from  the  filament  to  the  plate, 
when  the  filament  is  heated  for  the  device  to  be  actuated, 
whether  it  be  a  telephone  receiver,  an  amplifier  circuit,  a 
recorder  or  other  instrument.  The  filament  battery,  in  the 
case  of  the  more  common  vacuum  tubes,  is  a  6-volt  bat- 
tery although  there  are  special  vacuum  tubes  which  oper- 
ate on  lower  voltages.  A  special  tube  used  on  certain 
Westinghouse  receiving  sets  operates  on  a  single  dry  cell, 
or  about  1.4  volts  at  the  outside,  and  draws  but  l^ 
ampere  of  current.  The  usual  vacuum  tube,  such  as  the 
Radiotron,  requires  close  on  to  6  volts  and  a  trifle  over  1 
ampere.  Another  standard  tube,  known  as  the  A-P  tube, 
requires  not  more  than  5  volts  and  about  .7  ampere. 
This  means  that  dry  cells  are  quite  extravagant  in  this 
connection,  since  with  a  drain  of  about  one  ampere, 
any  dry  cell  will  not  last  very  long.  If  dry  battery  must 
be  used,  it  is  well  to  employ  two  sets  of  five  cells  each, 
the  two  sets  being  connected  together.  In  other  words, 
the  five  cells  of  each  battery  are  arranged  in  series,  with 
the  carbon  of  one  cell  connected  to  the  zinc  of  the  other, 


122  RADIO  FOR  EVERYBODY 

and  then  the  end  carbons  of  both  sets  are  connected  to- 
gether for  one  side  of  the  combined  battery,  and  the 
zincs  of  both  sets  are  connected  together  for  the  other 
side  of  the  combined  battery.  This  virtually  means  a 
battery  of  .twice  the  life  of  a  single  b-attery,  although  the 
voltage  remains  the  same.  The  name  of  this  arrangement 
of  batteries  is  series-parallel. 

Still,  there  is  nothing  that  really  takes  the  place  of  the 
storage  battery  in  operating  vacuum  tubes.  This  is  espe- 
cially true  where  more  than  one  vacuum  tube  is  being- 
used,  such  as  when  using  one  or  two  stages  of  amplifica- 
tion, as  is  explained  in  the  following  chapter.  The  storage 
battery  may  be  of  any  standard  type,  although  since  the 
heavy  demand  for  radio  equipment  began  some  few 
months  back,  there  have  appeared  several  special  storage 
batteries  particularly  intended  for  radio  work.  These 
storage  batteries  are  characterized  by  all-rubber  cases, 
eliminating  the  possibility  of  leakage  from  cell  to  ground 
or  from  cell  to  cell,  and  doing  away  with  one  of  the  most 
frequent  causes  of  noisy  sets.  Furthermore,  such  batteries 
are  of  a  smaller  ampere-hour  capacity  than  those  used  for 
automobile  starting  and  lighting  service,  thus  making  them 
lower  in  cost  and  more  convenient  to  handle  and  recharge. 

A  storage  battery  must  be  recharged  when  it  runs  down. 
In  a  subsequent  chapter  we  shall  consider  the  care  and 
recharging  of  the  storage  battery.  Suffice  it  to  state  that 
where  a  radio  set  employs  several  vacuum  tubes,  so  that 
the  drain  on  the  storage  battery  is  considerable,  it  pays 
good  dividends  to  install  some  form  of  recharging  ap- 
paratus. In  this  manner  the  storage  battery  may  be  re- 
charged whenever  necessary,  at  a  minimum  of  expense 
and  without  losing  valuable  time. 

Aside  from  the  storage  battery  for  the  filament,  a  "B" 
battery  must  be  provided.  This  battery  must  be  a  high- 
voltage  one.  In  the  early  days  of  vacuum  tubes  a  number 
of  flash-lamp  batteries  were  connected  together  so  as  to 
obtain  the  necessary  current,  but  today  there  are  special 
dry  "B"  batteries  put  up  in  compact  units  of  22^^  volts 


RADIO  FOR  EVERYBODY 


12: 


each.  These  **B"  battery  units  come  in  a  small  size  and 
a  large  size.  If  the  receiving  set  is  to  be  used  at  regular 
intervals,  it  is  the  part  of  better  judgment  to  buy  the 
larger  size.  A  single  ''B"  battery  unit  is  necessary  for 
a  vacuum  tube  detector  circuit,-  and  two  units  are  neces- 
sary if  an  amplifier  is  also  used  with  headsets,  and  three 
or  four  units  if  a  loud-speaker  is  employed,  as  will  be 
explained  in  the  next  chapter  devoted  to  amplifier  circuits. 
The  dry  '^B"  batteries  come  in  two  types,  aside  from 


GL 


m 


60 


TO    TUNER 


-=-"6" 


Principle  of  vacuu>m  tube's  operation:  GLi — Grid  leak; 
CC — condenser ;  F — filament ;  G — grid ;  P — plate ;  VT — vacuum 
tube;  "A" — Storage  battery  for  operating  vacuum  tube  fila- 
ment; R — rheostat  for  filament  current;  "B" — ^high  voltage 
"B"    battery    or    plate    battery,    and    telephones. 


the  two  sizes.  There  is  the  fixed  voltage  type,  in  which 
two  leads  or  terminals  give  the  full  voltage  of  the  battery, 
and  there  is  a  variable  voltage  type,  in  which  lugs,  binding 
posts,  or  holes  and  plugs  permit  of  using  a  number  of 
different  voltages.  The  variable  type  is  especially  useful 
in  using  certain  types  of  vacuum  tube  with  which  the  ''B" 
voltage  must  be  carefully  adjusted.  When  it  comes  to 
amplifier  tubes,  the  "B"  voltage  may  be  anything  from 
45  volts  up. 

There  are  also  available  special  low-capacity  high  voltage 


124 


RADIO  FOR  EVERYBODY 


storage  batteries,  which  may  be  used  in  place  of  the  dry 
battery  units  when  a  set  is  subjected  to  extensive  use. 
Such  storage  batteries  may  be  readily  recharged  and  their 


Inexpensive    receiving:    set    making    use    of    a    variometer    tuner 
and    a    crystal    detector.      Such    a    set    is    good    for    a    range    of 
25    miles,    perhaps    a    little    more,    when    receiving    radio-phone 
.    programs! 


operating  cost  must  of  necessity  be  lower  than  when  using 
dry  batteries,  which,  when  discharged,  are  worthless  and 
must  be  thrown  away. 

Often  the  question  is  asked :     Why  is  it  not  possible  to 
use  the  usual  lighting  current  for  operating  vacuum  tubes. 


RADIO  FOR  EVERYBODY  125 

The  fact  of  the  matter  Is  that  we  are  deahng  with  dehcate 
fluctuations  in  the  vacuum  tube.  If  the  filament  voltage 
should  vary  even  in  the  slightest  degree,  the  electronic 
flow  would  likewise  vary  and  cause  a  corresponding  noise 
in  the  telephone  receivers.  Therefore,  for  absolutely  quiet 
operation  it  is  necessary  to  employ  a  steady  and  positive 
flow  of  current  such  as  can  only  be  supplied  by  a  battery. 
Lighting  current,  whether  of  the  alternating  or  direct 
variety,  could  readily  be  reduced*  down  to  six  volts,  but  in 
either  case  there  is  a  distinct  "hum"  which  would  be  con- 
stantly heard  in  the  tekpho-ne  receivers  and  which  would 
drown  out  the  delicate  radio  signals.  Hence  lighting  cur- 
rent is  out  of  the  question. 

A  Vacuum  Tube  for  Every  Purpose 

It  is  well  to  remember  that  all  vacuum  tubes  are  not 
identical,  nor  are  they  absolutely  interchangeable.  They 
may  look  alike  if  they  are  of  the  same  size  and  kind,  but 
there  may  be  slight  differences  in  internal  dimensions  and 
degree  of  vacuum  or  gas  content  which  are  not  apparent 
even  upon  close  examination. 

Thus  the  type  now  in  most  general  use  is  classed  as  a 
soft  or  gas  content  tube  and  requires  a  critical  adjustment 
of  both  the  "B"  or  plate  voltage  and  the  "A"  or  filament 
current.  Tubes  of  this  type  are  extremely  sensitive  when 
properly  adjusted.  The  variation  of  the  filament  current 
is  accomplished  by  means  of  a  variable  resistance  or  rheo- 
stat placed  in  series  with  the  filament  lighting  battery.  In 
some  receiving  sets  the  rheostat  may  be  calibrated  in  ohms 
or  even  in  plain  divisions,  but  in  most  sets  it  is  not  cali- 
brated at  all,  a  simple  arrow  indicating  in  which  direction 
to  turn  the  knob  in  order  to  increase  the  voltage  or 
brighten  the  filament.  The  "B"  or  plate  voltage,  on  the 
other  hand,  is  variable  in  steps  of  1^  volts,  by  means  of 
a  variable  voltage  "B"  battery  as  already  described.  The 
proper  terminal  or  lug  or  plug  hole  of  the  "B"  battery  is 
found  by  experiment,  and  no  further  adjustment  is  re- 
quired for  a  long  time  to  come.    The  majority  of  vacuum 


126 


RADIO  FOR  EVERYBODY 


tube  detectors  operate  best  on  ''B"  voltages  between  16^ 
and  22^,  and  this  range  is  covered  by  the  variations  pro- 
vided  on   the   various   types    of   variable   plate  batteries. 


pp 

1 

RHEOST/V| 

/ 

^B- VACUUM 

^Sli^^ 

Pi|P^^^^W*"^^^w| 

p 

K-TUNiNG 
R-     DIAL  AMD 
W         HANDLE 

■ 

/ 

A  medium-priced  receiving  set  making  use  of  a  special  vacuum 

tube   whicli    operates    on    a   single    dry   cell,   instead   of  a   6-volt 

storage   battery. 


However,  there  is  no  harm  in  using  a  fixed  voltage  "B" 
battery,  except  that  the  best  results  are  not  likely  to  be 
obtained  except  if  the  tube  should  happen  to  be  one  that 
works  best  on  22^  volts. 


RADIO  FOR  EVERYBODY  127 

Amplifier  tubes,  which  look  just  like  the  detector  tubes 
and  cannot  be  told  apart  except  by  testing  their  electrical 
characteristics,  are  not  critical  in  adjustment  when  com- 
pared with  detector  tubes,  and  they  will  operate  success- 
fully on  plate  voltages  of  40  to  80  volts.  Where  a  detector 
and  two-stage  amplifier  combination  is  used,  three  or  four 
22^  volt  units  may  be  connected  in  series,  and  connections 
to  the  receiver  are  made  in  a  manner  which  permits  the 
use  of  the  full  voltage  on  the  amplifier  tubes,  while  a 
variable  portion  of  the  same  battery  is  used  for  the  de- 


VARIABLE 
CONDENSER 

Rear  view  of  a  simple  receiving  set  vphich  makes  use  of  a      simple 
inductance  and  a  variable  condenser,  as  well  as  a  crystal  detector. 

tector  tube.  Where  extremely  loud  signals  are  desired 
plate  voltages  of  100  or  over  may  be  used  without  damag- 
ing the  amplifier  tubes,  but  the  use  of  this  voltage  increases 
tube  noises  and  is  therefore  not  desirable  when  receiving 
signals  with  the  telephone  head  set.  However,  this  infor- 
mation is  only  included  here  as  part  of  the  receiver  prob- 
lem, and  more  will  be  said  about  amplifying  tubes  in  the 
next  chapter  devoted  exclusively  to  amplifiers. 


128 


RADIO  FOR  EVERYBODY 


A  detector  tube  which  does  not  prove  to  be  critical  as 
to  plate  voltage  and  filament  current  is  usually  defective. 
A  good  detector  tube  will  give  greatly  increased  signal 
strength  with  a  certain  plate  potential  and  filament  bril- 


RYSTAL     DETECTOR 


VARIABLE 
CONDENSER 


NDUCTANCE 
CONTROL  TtLEPHONE 

JACK 


Front  view  of   receiving  set    shown  on   page   127.      The   cabinet   of 
this   set  is  made  of  metal  instead    of  the   usual   wood. 


liancy.  An  amplifier  tube  which  requires  a  critical  plate 
voltage  or  filament  current  adjustment  will  not  give  satis- 
factory results  as  an  amplifier.  Tubes  of  this  character 
will  generally  be  found  useful  as  detectors.  In  certain 
receiving  sets  which  include  an  amplifier,  it  is  sometimes 


RADIO  FOR  EVERYBODY  129 

found  that  amplifier  tubes  are  recommended  for  use 
throughout,  for  the  reason  that  the  wiring  provides  for  a 
common  plate  voltage  and  filament  current  adjustment. 
Such  practice  may  simplify  the  construction  and  operation 
of  the  set,  true,  but  from  the  standpoint  of  efficiency,  it  is 
mighty  poor  business.  A  soft  or  gassy  tube,  known  as  a 
detector  tube,  should  be  used  for  the  detector,  and  a  hard 
tube  should  be  used  for  amplifying.  These  tubes,  while 
they  may  look  alike,  are  by  no  means  interchangeable, 
except  where  the  best  results  are  not  expected  or  de- 
manded. 

Having  been  introduced  to  the  vacuum  tube  in  a  general 
way,  we  can  now  return  to  receiving  sets  once  more.  The 
vacuum  tube  can  be  used  in  place  of  a  crystal  detector 
in  almost  any  circuit,  and  in  such  applications  it  will  prove 
a  considerable  improvement  over  the  latter.  Then,  by 
using  special  vacuum  tube  circuits,  especially  of  the  so- 
called  regenerative  variety,  which  will  be  described  later 
on  in  this  chapter,  the  sensitiveness  of  the  vacuum  tube  is 
so  much  superior  to  the  crystal  detector  as  to  make  a 
comparison  quite  out  of  order. 

The  wiring  scheme  already  shown  gives  the  fundamen- 
tals of  vacuum  tube  hook-ups  when  used  as  a  detector. 
It  will  be  noted  that  a  small  fixed  condenser  and  an  ex- 
tremely high  resistance,  known  as  a  grid  leak,  are  placed 
in  series  with  the  tuner.  Furthermore,  the  polarity  of 
the  connections  is  of  utmost  importance. 

Primary  and  Secondary  Circuits  and  How  They  Are 
Coupled 

So  far,  the  circuits  have  been  of  the  simplest  type,  with 
a  physical  connection  between  the  aerial-ground  circuit 
and  the  closed  circuit,  known  as  the  oscillating  circuit,  in 
which  the  detector  is  placed.  Now  for  reasons  which  need 
not  be  explained  here,  since  this  work  does  not  attempt 
to  concern  itself  with  the  theories  or  the  mathematics  of 
radio  but  rather  with  the  application  of  the  results,  many 
sets   make   use   of   distinct   aerial-ground   and   oscillating 


130 


RADIO  FOR  EVERYBODY 


Loose-coupler  of  the  old  type 

which   has   now    become   more 

or    less    obsolete. 


circuits,  with  no  physical  connection  between  them.  Trans- 
ference of  energy  between  the  former  and  the  latter  is 
effected  by  means  of  two  windings  which  are  brought  into 
more  or  less  close  inductive  relation.  In  one  form  these 
windings  are  known  as  a  loose-coupler,  in  another  they 

form  a  vario-coupler,  still  an- 
other arrangement  calls  for 
compact  coils  held  in  hinged 
holders  so  that  they  may  be 
swung  towards  or  away  from 
each  other. 

The  loose-coupler  is  the 
forerunner  of  the  v  a  r  i  o  - 
coupler  and  the  compact  coil 
arrangement.  It  consists  of  a 
large  tube  on  which  are  wound 
many  turns  of  wire,  which  is 
the  primary  and  is  connected  with  the  antenna  and  the 
ground,  and  a  smaller  tube,  which  slides  in  and  out  of  the 
large  tube  and  is  wound  with  many  turns  of  wire.  Some 
means,  such  as  a  slider  or  a  multi-point  switch,  is  generally 
employed  to  vary  the  number 
of  active  turns  in  both  the  pri- 
mary and  secondary  of  the  loose 
coupler. 

In  keeping  with  modern  prac- 
tice, which  has  done  away  with 
sliding  arrangements  in  favor 
of  rotary  adjustments,  the  vario- 
coupler  has  become  the  stand- 
ard device  for  coupling  the 
primary  and  secondary  circuits 
of  a  receiving^  set.     The  vario- 

t         1  J.    u  J        vt,    Vario-coupler,      which      has 

coupler   has   a   tube   wound   with    taken    the    place    of    the    old 

many   turns   of    wire,    forming  *yp«  loose-coupier. 

the  primary  or  antenna-ground  circuit,  and  a  wooden 
ball  or  composition  frame,  which  is  mounted  on  a  rotable 
shaft  and  is  also  wound  with  many  turns  of  wire  to  form 


RADIO  FOR  EVERYBODY 


131 


FT 


T^ 


How    a    loose-coupler     or    vario- 

coupler  is  introduced  in  a  crystal 

receiving    set.      In    tliis    instance 

the  primary  is  adjustable. 


the   secondary   or   the   oscillating 

circuit  member. 

The  accompanying-  diagrams 
indicate  better  than  words 
how  the  loose-coupler, 
vario-coupler,  or  inductance 
coil  mounting  may  be  em- 
ployed in  connection  with  a 
vacuum  tube  or  a  crystal 
detector.  Obviously  the 
vacuum  tube  is  to  be  used 
wherever  possible.  There 
are  also  given  several  cir- 
cuits in  which  fixed  in- 
ductance units,  vario-meters 
and     condensers     are     em- 


ployed.  The  radio  amateur 
soon  learns  to  arrange  and  re- 
arrange his  receiving  equip- 
ment until  he  obtains  the  best 
results — if  he  is  ever  satisfied. 

Inductance  in  Small  Packages 

The  tuning  coil  has  more  or  less 
become  obsolete,  and  in  its  place 
we  find  more  compact  forms  of  in- 
ductance. One  of  these  later-day 
forms  is  a  single  layer  of  wire 
wound  on  a  tube,  after  the  fashion 
of  'the  tuning  coil,  but  having  a  mul- 
ti-point switch  connected  with  vari- 
ous numbers  of  turns,  in-  using  a  loose-coupler  or  Tario- 
(iff^:^c\  ni  n  ^lirlpr     TVipn  tViPrp       coupler     in     connection     with     a 

steaa  01  a  snaer.    i  nen  mere     variometer  and  a  variable  con- 
are    the  compact   mductance       denser  for  increasing  or  decreas- 
•1  1  ^^  T\  ing     the     antenna     circuit     w^ave 

coils,    such   as    the    Duo-        ^  length. 


132 


RADIO  FOR  EVERYBODY 


Lateral  and  the  Honeycomb  types,  which,  while  fixed  as 
regards  their  wave  length  values,  are  used  interchangeably 
so  that  the  operator  can  readily  shift  from  one  coil  to 
another  and  thus  vary  the  wave  length  in  big  steps,  de- 
pending on  a  variometer  or  a  variable  condenser  for  the 
finer  tuning. 

Second  only  to  the  development  of  the  vacuum  tube,  the 
concentrated  inductance  has  marked  a  new  era  in  radio. 
Prior  to  'the  war  there  were  in  general  use  the  huge,  bulky, 
single-layer  inductance  coils  then  so  closely  identified  with 

long-wave  recep- 
tion. Compact  re- 
ceiving sets,  sim- 
p  1  e  adjustments, 
and  the  neatness 
that  goes  with 
small  units,  were 
not  to  be  thought 
of  because  of  the 
bulkiness  of  the 
inductance  then 
employed. 

The  demand  for 
compactness  and 
simplicity,  to- 
gether with  the 
far  greater  effi- 
ciency and  prac- 
ticability, on  the 
part  of  the  war- 
ring nations,  called  for  a  radical  change  in  inductance  de- 
signs. As  a  consequence,  so-called  bank-wound  coils  were 
employed  to  an  increasing  extent,  followed  soon  after  by 
the  present  types  of  concentrated  inductances.  Today 
practically  all  receiving  sets  with  a  long-wave  capacity 
are  provided  with  these  compact  inductance  units  since  a 
long  wave  length  can  be  obtained  in  a  very  small  space. 
Special  mountings  have  come  into  use  for  these  compact 


One   style  of  mounting   which  takes  two  or 
three   compact  inductance  coils  for  a  loose- 
coupler,   and   tickler   coil   combination   when 
using  a  regenerative  circuit. 


RADIO  FOR  EVERYBODY  133 

inductance  coils.  The  usual  method  is  to  mount  the  coils 
on  a  block  by  'means  of  a  fiber  band  which  passes  around 
the  coil  to  hold  it  in  place.  The  block,  in  turn,  is  provided 
with  bayonet  plugs  so  that  it  can  be  readily  plugged  into 
a  circuit.  A  loose-coupler  arrangement  is  effected  by 
means  of  a  stand  which  permits  of  moving  the  coils 
towards  or  away  from  each  other,  and,  in  some  cases,  even 
turning  one  of  the  coils  from  the  vertical  to  the  horizontal 
position. 

Another  form  of  compact  inductance  is  known  as  the 
spider-web  inductance.  This  consists  of  a  sheet  of  in- 
sulating material  in  which  radial  slots  have  been  cut,  and 
the  wire  is  wound  spirally  in  and  out  of  these  slots,  so 
as  to  make  a  flat  or  pancake  inductance  unit.  Such 
inductance  units  can  be  used  as  a  loose-coupler  by  having 
one  fixed  and  the  other  hinged. 

The  Question  of  Telephone  Receivers 

Little  or  nothing  has  so  far  been  said  regarding  the 
telephone  receivers,  yet  here  is  an  important  member  of 
any  receiving  set.  In  fact,  no  matter  how  elaborate  a 
receiving  set  may  be,  if  the  receivers  are  not  of  the  best 
available  type,  the  results  are  not  as  good  as  they  might  be. 

Radio  telephone  receivers  are  not  just  ordinary  tele- 
phone instruments.  They  are  far  more  sensitive  than 
anything  which  is  ever  used  in  regular  wire  telephony. 
First  of  all,  they  are  constructed  with  the  utmost  care; 
secondly,  they  have  windings  of  very  fine  wire,  as  com- 
pared with  'the  relatively  large  wire  used  in  the  ordinary 
telephone  receiver.  Thirdly,  the  diaphragm  of  the  usual 
wireless  receiver  is  far  thinner  and  therefore  more  delicate 
than  that  used  in  the  ordinary  telephone  receiver. 
Fourthly,  in  certain  types  of  wireless  receivers  the  two 
receivers  of  a  head  set  are  matched  in  tone,  so  that  both 
ears  receive  precisely  the  same  sounds.  This  feature 
makes  for  the  utmost  response  on  the  part  of  the  ears, 
and  therefore  the  best  signals. 

Xo  matter  how  inexpensive  a  receiving  set  may  be,  it 


134  RADIO  FOR  EVERYBODY 

is  poor  business  to  economize  on  the  telephone  receivers ; 
for  it  is  a  fact  that  a  receiving  set  is  no  better  than  its 
telephone  receivers.  The  telephone  receivers,  after  all,  are 
the  final  link  in  the  chain  of  reception;  they  comprise  the 
agency  which  actually  conveys  the  radio  signals  or  music 
or  what  not  to  the  operator's  ears,  and  as  such  they  can 
add  to  or  detract  from  the  receiving  set  as  a  whole. 


ADJUSTABLE    INDUCTANCE 
^                     COtL 

i 

l#^ 

HFjV 

WfNOOW     FOR     DETECTOR  TUfiEs! 

H 

/          WINDOWS     FOR    AMPUIFIER: 
/                                  TUBES                               1 

PRIMARY         ^^*^*^S^S! 

s 

^^Hj^^^^^^^^^^^^^'x  .'"7^"-^''-^'^ 

SECONDARY 
CONDCNSEK 

PLUG    FOR 

TELE. 

^HOM£S                '''illlllllllf^ 

Receiving:   set   in  wliich   three   compact   inductance  coils,   adjusta- 
bly mounted  on   top'  of  cabinet,   permit   of   variable   coupling  and 
regenerative    action.      The   unit    at   right   is   the   vacuum    tube    de- 
tector and  two-stage  amplifier. 

Of  radio  telephone  receivers,  there  are  various  types 
and  special  merits  are  claimed  for  each  type,  as  might 
well  be  expected.  However,  there  is  one  fact  that  applies 
to  all  types,  and  that  is  the  care  with  which  a  really  good 
receiver  must  be  constructed.  That  is  why  the  better 
offerings  cost  considerably  more  than  others ;  and  it  will 
generally  be  found  that  the  better  offerings  are  well  worth 
the  extra  cost.  If  the  radio  amateur  does  not  feel  he  can 
afford  the  better  kind  of  telephone  receivers,  he  can  at 
least  start  with  an  inexpensive  pair,  and  later  on  go  to 
the  better  kind,  experiencing  thereby  considerable  pleasure 


RADIO  FOR  EVERYBODY  135 

in  the  increased  range  and  clearer  signals  or  telephone 
messages  which  he  obtains  with  his  receiving  equipment. 
Certain  types  of  receivers  have  been  carefully  matched 
for  tone  and  pitch,  and  respond  loudly  to  signals  over  a 
wide  range  of  frequencies,  especially  those  of  high  pitch, 
thus  permitting  reception  that  would  not  be  possible  with 
inferior  head  sets  that  do  not  respond  to  signals  of  high 
frequency.  Other  types  have  two  solenoids  wound  on  the 
pole  pieces  of  a  laminated  permanent  magnet  which  acts 
upon  an  iron  reed  fastened  to  a  conical  aluminum 
diaphragm.     The  reed   is   adjustable  and,   therefore,   the 


^ 

^^COMPACT     INOUCTAMCE      COW. 

CRV5TAL   DETE.CTOR  S^ 

raB  TUNING     DIAL 

Sm 

i   .'  I!!  ^  ' 

^ — X 

''K 

'  Q 

FILAMENT 
"RHEOSTAT 

f^0t^ 

"t".* 

{.^^^SmL  i 

«v  ^    ..    « 

l^    %    /       ,„       ■ 

^^k...^ 

i^'.-liie 

•«'»^.,€      ©      '' 

^^m 

MEAD    PM0NE5                 ^^'^■■B 

^1^0^-  Y 

^mk 

'■""'                TELEPHONE     PLUG 

Receiving  set  making  use  of  compact  inductance  coils  for  rapidly- 
changing    the    wave    length    range    in    erg    steps.      The    unit    at 
right   is  the   vacuum   tube  detector. 

reed  note  can  be  made  identically  the  same  in  both  ear 
pieces  to  coincide  with  the  spark  frequency  of  incoming 
signals  or  what  is  known  as  the  beat  frequency.  An  ad- 
justment screw  is  mounted  on  the  back  of  each  receiver 
case  and  is  designed  so  that  excess  adjustment  cannot  be 
made.  The  diaphragm  is  of  unusual  design,  being  of  a 
conical  shape  with  greater  thickness  toward  the  center. 
This  design  is  said  to  result  in  improved  reproduction. 


136 


RADIO  FOR  EVERYBODY 


There  is  still  another  type  of  wireless  telephone  receiver 
in  which  a  solenoid  winding  is  mounted  in  such  a  manner 
with  relation  to  the  long  permanent  magnet   within  the 


A  single  circuit  tuner  making  use  of  a  variometer  and  a  variable 
condenser,  as  well  as  a  tickler  for  regenerative  effects.  The 
general  tuning  is  done  with  the  first  handle,  the  fine  tuning 
with  the  lower  left-hand  knob,  and  the  regenerative  effect  is 
controlled    with    the    lower    right-hand    knob. 


case  as  to  actuate  an  armature  which  connects  with  a  mica 
diaphragm.     The  slightest  current  variations  throughout 


RADIO  FOR  EVERYBODY 


137 


the  solenoid  windings  will  actuate  the  armature  which  in 
turn  vibrates  the  diaphragm. 

With  all  receiving  sets,  whether  of  the  crystal  or  the 
vacuum  tube  type,  it  is  generally  impossible  to  use  a  loud- 


i 

^^"^^^^^1^     TEUEPHONE 
^lll      HEAD- SET 

^I^Mr  '-^^F^^LvACUUM-TUSES 

Companion  unit  to  tuner  siiown  on  preceding  page.  This  unit  is 
the  vacuum  tube  detector  and  two-stage  amplifier.  The  two  knobs 
are  the  rheostat  controls  for  the  detector  and  amplifier  tube  fila- 
ments. The  telephone  plug  may  be  inserted  in  one  of  three  holes 
or  jacks,  if  detector  only,  one  stage  or  two  stages  of  amplifica- 
tion are  desired. 

speaking  telephone — an  instrument  equipped  with  a  horn 
that  projects  loud  sounds  throughout  a  large  room,  thus 
making  the  use  of  telephone  head  sets  unnecessary.  A 
loud-speaker  must  be  operated  by  means  of  an  ampHfier, 


138 


RADIO  FOR  EVERYBODY 


and  this  phase  of  radio  reception  will  be  described  in  the 
next  chapter.  It  occasionally  happens  that  nearby  trans- 
mitters are  received  so  loudly  that  they  may  be  heard 
some  distance  away  from  the  telephone  receivers.  Under 
such  circumstances,   it  is   obviously  possible  to  attach  a 


Regenerative  set  making  use  of  tickler  coil.  P — primary  of 
Tario-coupler ;  TIC — tickler  coil;  VCl — variable  condenser  for 
varying-  antenna-ground  wave  length;  VC3 — variable  con- 
denser for  varying  secondary  of  vario-coupler ;  GLi — grid 
leak;  GC — grid  condenser;  VT — vacuum  tube  detector;  B — 
high  voltage  or  plate  battery;  FC — fixed  condenser;  T — 
'phones.  The  dotted  line  indicates  how  wiring  would  run 
for  an  ordinary,  non-regenerative  set. 


horn  to  a  telephone  receiver  and  thus  have  an  improvised 
loud  speaker,  but  this  is  certainly  the  rare  exception  rather 
than  the  general  rule. 

Regenerative  Reception  or  Self  Amplification 

So  far,  the  various  receiving  layouts  or  hook-ups  have 
brought  the  radio  frequency  energy  right  to  the  detector, 
which  in  turn  rectified  it  and  passed  it  on  to  the  telephone 
receivers.  Now  if  the  energy  which  is  about  to  be  passed 
on  to  the  telephones  is  partly  re-impressed  on  the  grid 
of  the  vacuum  tube,  it  will  add  materially  to  the  voltage 
of  the  incoming  signal.  This  will  naturally  give  a  greater 
charge  on  the  grid,  and  consequently  a  greater  variation 


RADIO  FOR  EVERYBODY 


139 


of  plate  current,  which  in  turn  means  louder  signals.  In 
this  manner  the  sensitiveness  of  the  vacuum  tube  is  greatly 
increased ;  indeed,  it  is  operating  as  a  detector  and  an 
amplifier  combined.  This  practice  is  known  as  the  regen- 
erative or   feed-back  reception. 

But  how  is  the  plate  energy  re-impressed  on  the  detec- 
tor? There  are  two  methods  in  general  use  for  obtaining 
the  regenerative  effect.  The  first  makes  use  of  what  is 
known  as  the  tickler — an  extra  coil  which  is  brought  near 
the  inductance  or  winding  of  the  detector  or  oscillating 
circuit.  Thus  the  simplest  type  of  regenerative  receiver 
consists  not  of  two  compact  inductance  coils  but  of  three 
coils,  adjustably   mounted,  as   shown  in  the  diagram  on 

f  A 


ri 


VCt 


\- 


R. 


FC 
-<o)Jo)-l 


Another  method  of  obtaining  regrenerative  results.  A — 
antenna;  P — primary;  S — secondary,  of  the  vario-coupler  C; 
VCl — variable  condenser  in  antenna-ground  circuit;  VI — 
variometer;  GL. — grid  leak;  VC2 — variable  condenser  as  grid 
condenser;  VT — vacuum  tube  detector;  V2 — plate  variometer 
for  feed  back;  FC — fixed  condenser;  T — telephones;  "B" — 
high  voltage  or  plate  battery;  R — filament  rheostat;  Kl — 
high  voltage  battery  rheostat. 


page  138.  The  first  coil  is  the  primary,  connected  with 
the  aerial-ground  circuit  as  already  mentioned,  and  the 
second  is  the  secondary,  connected  with  the  detector.  The 
third  is  the  tickler,  and  is  connected  in  the  plate  circuit, 
as  indicated  by  "TIC"  in  the  wiring  diagram.  The 
adjustment  between  the  tickler  coil  and  the  secondary  coil 
is  of  great  importance,  for  the  regenerative  effect  must 


MO  ^     RADIO  FOR  EVERYBODY 

often  be  regulated  to  obtain  the  best  results,  as  will  be 
explained  in  the  chapter  on  operating  radio  stations. 

The  tickler  coil  also  comes  in  handy  when  receiving  un- 
damped signals,  which,  as  explained  in  our  first  chapter,  do 
not  affect  the  simpler  types  of  receiving  sets  and  therefore 
cannot  be  detected.  With  the  tickler  it  becomes  possible 
to  adjust  the  coils  in  such  a  manner  that  the  detector 
begins  to  oscillate;  in  other  words,  it  is  generating  high 
frequency  current  on  its  own  account.  If  this  high  fre- 
quency current  is  modified  until  it  varies  but  slightly  from 
the  frequency  of  the  incoming  radio  wave,  then  there  will 
be  heard  in  the  telephone  receivers  the  difference  between 
the  two  frequencies.  For  instance,  if  the  incoming  radio 
wave  is  100,000  cycles  frequency,  the  detector  circuit 
can  be  adjusted  to  102,000  cycles  frequency,  and  there 
will  then  be  heard  in  the  telephone  receivers  a  note  of 
2,000  cycles,  which  is  clearly  audible.  The  note  detected 
is  known  as  the  ''beats,"  and  can  be  varied  in  tone  accord- 
ing to  the  adjustment  of  the  circuit  and  the  incoming 
frequency.  Obviously,  this  method  gives  almost  any  note 
desired,  therefore  the  transmitting  stations  received  in 
this  manner  do  not  have  a  characteristic  note  such  as  is 
obtained  by  other  methods  of  transmission  and  reception. 

Another  method  of  receiving  undamped  waves,  such  as 
are  sent  out  by  arc  stations,  is  to  employ  a  "tikker."  Such 
practice  is  only  resorted  to  with  a  plain  receiving  set,  such 
as  one  using  a  crystal  detector,  with  no  provision  for  set- 
ting up  local  oscillations  so  as  to  obtain  "beats."  This 
is  merely  some  means  of  breaking  up  the  incoming  high- 
frequency  wave  energy  so  that  it  becomes  audible  and 
therefore  can  be  detected  in  the  telephone  receiver.  One 
method  is  to  use  a  small  pulley  mounted  on  an  electric 
motor,  and  to  have  a  wire  resting  in  the  groove  of  the 
pulley.  When  undamped  waves  or  CW  signals,  as  they 
are  called,  come  through  such  an  arrangement,  they  are 
received  in  the  form  of  short  or  long  scratchy  sounds, 
because  of  the  tikker's  interruptions.  However,  a  tikker 
is  in  reality  an  imperfect  contact  and  as  such  it  takes  away 
from   the   strength   of   the   incoming   undamped   or   CW 


RADIO  FOR  EVERYBODY 


141 


signals.  Therefore  the  regenerative  arrangement  is  to 
be  preferred. 

Two  other  methods  in  general  use  for  regenerative 
reception  are  shown  in  the  accompanying  diagrams.  It 
will  be  noted  that  instead  of  a  tickler  coil,  use  is  made 
of  a  variometer  in  the  plate  circuit.  This  variometer 
serves  to  tune  and  feed  back  into  the  grid  the  added 
voltage  of  the  plate  circuit. 

All  regenerative  sets  are  delicate  to  operate,  for  the 
regenerative  effect  gives  rise  to  all  kinds  of  noises  in  the 
telephone  receivers  ranging  from  a  hissing  steam   sound 


itI'I'i  (3 


still  another  method  of  regenerative  operation:  A — antenna; 
P — primary;  S — secondary,  of  vario-coupler  C;  VCl — variable 
condenser  in  antenna-ground  circuit;  VC2 — variable  con- 
denser; VC3 — variable  condenser  used  as  grid  condenser; 
GLr — grid  leak;  "A" — filament  battery;  VT — vacuum  tube 
detector;  V — plate  variometer;  FC — fixed  condenser;  T — 
tePephones ;  "B" — high  voltage  or  plate  battery ;  R — plate 
battery  rheostat;  G — ground.  Note  the  extra  inductance 
coil  of  few  turns,  developed  by  experiment. 


to  the  babel  of  sounds  that  might  be  expected  in  a  monkey 
house  riot.  The  operation  of  such  a  set  is  considerably 
more  involved  than  the  plain  receiving  equipment,  but  on 
the  other  hand  the  self -amplifying  feature  greatly  adds  to 
the  results.     Furthermore,  it  is  necessary  to  use  metallic 


142 


RADIO  FOR  EVERYBODY 


shields  between  the  operator  and  the  components  of  the 
regenerative  set,  since  the  capacity  of  the  body  of  the 
operator  materially  affects  the  delicate  adjustments  of  the 
regenerative  set.  Most  of  the  better  regenerative  instru- 
ments are  provided  with  metallic  shields  inside  the  cabi- 
nets, so  as  to  reduce  the  body  capacity  trouble  to  a  mini- 
mum. In  other  instruments  the  dials  are  of  metal  and 
are  grounded  to  act  as  shields. 

GL 


Another  method  of  obtaining  a  regenerative  receiver.  L. — 
loose-coupler  or  vario-coupier;  VC — variable  condenser  in  pri- 
mary circuit;  VI — variometer  in  grid  circuit;  GL — grid  leak; 
A — filament  battery;  R — filament  rheostat;  B — '*B"  or  plate 
battery;  FC — fixed  condenser;  T — telephones;  V3 — plate  or 
"feed-back"  variometer;    G — ground. 


There  is  virtually  no  end  to  the  different  arrangements 
which  can  be  followed  in  receiving  radio  signals.  The 
wiring  diagrams  shown  in  the  foregoing  pages  are  only 
intended  as  a  preliminary  guide,  and  are  offered  as  sug- 
gestions to  the  beginner.  As  one  becomes  more  proficient 
and  versed  in  the  radio  art,  one  soon  learns  other  arrange- 
ments which  may  prove  more  interesting  and  efficient. 


Chapter  V. 

OPERATING  THE  RADIO  RECEIVING 

SET  AND  MASTERING  THE 

TELEGRAPH  CODE 


THE  day  may  arrive  when  the  radio  receiving  sets, 
capable  of  receiving  clear,  loud  music  from  distant 
points,  will  be  reduced  to  the  simplicity  of  the  phono- 
graph. For  the  present,  however,  simplicity  exists  only 
in  the  inexpensive  receiving  sets,  which  are  intended  for 
the  reception  of  radio  telephone  and  telegraph  signals  at 
short  range.  When  it  comes  to  receiving  sets  for  ranges 
of  25  miles  or  more,  good  results  can  only  be  obtained 
with  elaborate  apparatus.  And  the  more  elaborate  the 
apparatus  becomes,  the  greater  the  care  and  skill  required 
for  its  successful  operation. 

Take  the  simple  receiving  sets,  for  example.  There 
is  little  or  nothing  to  master  in  the  way  of  operation.  Such 
sets  generally  have  a  multi-point  switch  for  controlling 
the  wave  length,  and  a  crystal  detector.  The  crystal  de- 
tector must  be  accurately  adjusted  for  the  utmost  sen- 
sitiveness, and  this  requires  a  little  care.  The  crystal  used 
in  such  a  detector  is  not  of  uniform  sensitiveness  through- 
out, hence  the  little  metal  point  or  the  fine  wire,  making 
contact  with  the  crystal,  must  he  shifted  about  until  a 
sensitive  spot  is  obtained. 

At  almost  any  hour  of  the  day  there  is  a  radio  telegraph 
station  working  within  range  of  the  simplest  receiving 
set,  unless  the  latter  happens  to  be  located  in  some  very 
remote  spot.     In  that  event,  the  simple   set  should  not 


144  RADIO   FOR  EVERYBODY 

have  been  selected  in  the  first, place,  for  its  radio  telegraph 
range,  as  a  rule,  is  certainly  no  more  than  50  to  100  miles, 
while  its  radio-phone  range  is  less  than  25  miles.  In  this 
connection  it  is  well  to  point  out  that  many  persons  have 
been  and  are  buying  little  $15.00  receiving  sets  for  use  in 
some  remote  part  of  Canada  or  Texas  or  Montana  or 
some  other  section  far  removed  from  the  existing  radio- 
phone broadcasting  stations,  and  are  surprised  and  bitterly 
disappointed  at  not  receiving  the  music  and  talks  which 
they  have  read  so  much  about.  Alost  radio  manufacturers 
are  careful  not  to  sell  their  instruments  under  such  circum- 
stances, for  they  realize  that  disappointments  of  this 
nature  only  result-  in  giving  the  public  a  wrong  impres- 
sion of  radio,  which  may  persist  despite  all  future  efforts 
to  explain  why  they  failed  in  their  first  attempt. 

At  any  rate,  if  a  person  is  located  well  within  the  range 
of  radio  telegraph  and  radio  telephone  stations,  the  crystal 
detector  can  be  readily  adjusted.  While  listening  with 
the  telephone  receivers,  the  operator  shifts  the  little  point 
or  wire  about  on  the  crystal.  If  there  is  a  radio  telephone 
or  telegraph  station  working  within  range,  one  soon  hears 
the  music  or  talk  or  again  the  short  and  long  buzzes,  as 
the  case  may  be.  There  may  be  no  trasmitter  operating 
at  the  time,  and  no  sounds  will  be  heard.  For  this  reason, 
it  is  sometimes  necessary  to  use  some  simple  form  of 
tester  to  determine  the  sensitiveness  of  the  detector, 
without  depending  on  actual  signals. 

Is  THE  Crystal  Detector  Sensitive? 

When  the  crystal  detector  is  adjusted  properly.  It 
should  respond  to  disturbances  other  than  actual  radio 
waves.  Thus  in  the  city,  where  there  are  electric  light 
wires,  telephone  lines,  trolley  cars,  elevators  and  other 
electrical  appliances  and  machinery,  the  detector  should 
respond  to  the  electromagnetic  waves  given  off  by  elec- 
trical machinery  of  all  kinds  within  range.  In  other 
words,  if  the  detector  remains  absolutely  silent,  then  it  is 
evident  that  no  sensitive  spot  has  been  found;  but  if  it 
causes  clicks,  scratchy  sounds,  buzzes  and  other  noises  to 


RADIO   FOR   EVERYBODY 


145 


be  heard  in  the  telephone  receiver,  then  it  may  be  taken 
for  granted  that  the  detector  is  satisfactorily  adjusted. 
Sometimes  the  sensitiveness  may  be  tested  by  turning  on 
and  off  a  nearby  electric  lamp.  This  should  produce  a 
loud  click  in  the  telephone  receiver.  However,  if  a  hum 
is  heard,  this  should  not  be  considered  as  an  indication  of 
the  sensitiveness  of  the  detector  adjustment.     Indeed,  the 

hum  is  caused  by  what  is 
known  as  induction,  given  off 
by  an  alternating  current  line. 
This  hum  may  be  picked  up 
when  the  point  or  wire  is  not 
even  pressing  on  the  crystal ; 
so  that,  far  from  indicating  a 


e\ 


A    combination    receiving    and     CW    transmitting     set    of    the 

inter-panel   type,   with   the   various   units    standardized   so    that 

they   can   be  assembled  to   form   any   desired   arrangement   for 

the    amateur    station. 

sensitive    detector,    it    should    indicate   that    the    detector 
members  are  not  even  in  proper  contact. 

For  those  desirous  of  making  sure  of  their  crystal 
detector  adjustment,  it  is  perhaps  best  to  use  what  is 
knowa  as  the  buzzer  test.  This  calls  for  a  small  buzzer, 
such  as  is  used  in  bell  circuits.  The  buzzer  is  connected 
in  the  usual  manner  with  a  push  button  and  cell  of  dry 
battery,  but  a  wire  is  brought  from  one  side  of  the  buzzer 
interrupter  to  the  ground  lead  of  the  receiving  set  to  be 
tested.     Then,  when  the  buzzer  is  operated,  the  electro- 


146  RADIO   FOR  EVERYBODY 

magnetic  waves  given  off  by  the  buzzer  interrupter  are 
impressed  on  the  radio  receiving  set  and  the  detector  can 
be  adjusted  for  sensitiveness  in  the  same  manner  as 
though  the  operator  were  Hstening  for  a  radio  transmitter. 
The  buzzer  test  is  still  used  in  some  forms  of  elaborate 
receiving  sets  which  include  a  crystal  detector,  for  the 
reason  that  it  serves  as  a  positive  indication  of  the  sen- 
sitiveness of  the  crystal  detector. 

For  the  general  run  of  radio  receiving,  however,  a 
buzzer  test  is  hardly  necessary.  If  a  crystal  detector  set 
is  being  used  well  within  the  range  at  which  such  appar- 
atus is  operative,  the  detector  can  soon  be  adjusted  while 
listening  to  actual  transmitters.  However,  if  the  crystal 
detector  receiving  set  is  being  used  beyond  the  usual  range, 
then  it  may  be  necessary  to  use  some  form  of  buzzer  test 
in  order  to  make  certain  that  the  detector  is  adjusted  to 
the  utmost  sensitiveness. 

As  for  the  tuning  of  simple  sets,  there  is  Httle  to  be 
said.  The  switch  handle  or  the  tuning  handle  is  moved 
about  until  the  desired  transmitter  is  intercepted.  With 
any  aerial  up  to  150  feet  long,  the  simple  set  should  give 
excellent  results.  However,  in  the  event  that  the  aerial 
is  over  150  feet  long,  or  that  a  long  lead-in  wire  has  had 
to  be  used  in  order  to  connect  the  antenna  with  the  receiv- 
ing set,  it  may  so  happen  that  the  natural  wave  length 
of  the  antenna  circuit  is  greater  than  that  of  the  desired 
radio-phone  or  radio  telegraph  waves.  In  such  instances 
a  fixed  or  variable  condenser  should  be  placed  in  series 
with  the  antenna  or  the  ground,  thus  reducing  the  wave 
length. 

While  it  is  desirable  to  keep  receiving  sets  as  simple 
as  possible,  especially  where  laymen  who  will  always  be 
laymen  are  concerned,  good  results,  more  particularly  at 
a  considerable  distance  from  the  transmission  station, 
can  only  be  obtained  with  fine  tuning  facilities.  Fortu- 
nately, one  soon  becomes  used  to  tuning  a  receiving  set, 
no  matter  how  many  handles  may  be  involved  in  the 
tuning  operation.  Even  with  a  tuning  coil,  the  operator 
soon  learns  just  where  to  place  the  single  o-r  double  sliders 


RADIO   FOR   EVERYBODY 


1¥> 


in  order  to  pick  up  any  given  radio  telephone  or  radio 
telegraph  station.     With  a  loose-coupler  tuner,  the  oper- 


Nothing:  is  simpler  tlian  erecting'  the  antenna  for  receiving  pur- 
poses. A  single  wire,  with  insulators  at  either  end,  is  run 
between  the  house  and  a  barn,  tree,  or  clothes  pole.  Then  a 
tap  is  taken  oflf  the  near  end  of  the  antenna  and  brought  into 
the  house.     This  is  known  as  the  lead-in. 


148 


RADIO   FOR  EVERYBODY 


It  is  best  to  pass  all  wires  through  porcelain  tubes  when  they 
enter  the  house,  as  shown  here,  even  thougrh  the  wires  may  be 
heavily  insulated.    It  is  an  additional  precaution  Avell  worth  taking* 

ator  soon  learns  how  to  adjust  the  primary  and  secondary 
circuits,  and  how  much  coupling  to  use.  With  condensers 
or  variometers,  the  operator  becomes  familiar  with  the 
adjustments  of  the  various  dials  for  picking  up  any  desired 
transmitter.  Indeed,  some  instruments  are  provided  with 
dials  that  have  plain  subdivisions,  without  numbers  of  any 
kind,  or  even  with  plain  pointers  and  blank  backgrounds ; 
yet  the  operator  soon  learns  just  where  to  place  the  dials 
or  pointers  in  order  to  obtain  the  desired  results. 

At  first,  the  operation  of  a  radio  receiving  set  is  apt  to 
be  a  little  complicated  and  possibly  disappointing,  for  the 
reason  that  the  operator  may  not  obtain  the  best  results 
immediately.  But  at  the  end  of  an  hour  or  two  the  oper- 
ator readily  masters  the  various  adjustments  and  knows 


RADIO   FOR   EVERYBODY  149 

just  where  to  place  the  dials  and  pointers  in  order  to  pick 
up  the  transmitters  which  he  wants  to  listen  in  on.  Fur- 
thermore, it  is  interesting  to  note  that  any  extensive 
change  in  the  antenna  varies  the  relative  adjustments  of 
the  receiving  set.  Thus  if  the  operator  is  accustomed  to 
a  giveil  antenna,  the  changing  of  the  proportions  of  that 
antenna  or  its  height  will  upset  the  previous  tuning  values 
and  the  operator  will  have  to  learn  his  adjustments  all 
over  again.  However,  much  of  the  fun  that  is  afforded 
by  radio  comes  in  learning  how  to  tune  the  receiving  set 
and  in  searching  for  new  transmitters. 

Installing  the  Receiving  Set 

In  a  way,  the  few  pointers  regarding  the  installation 
of  the  receiving  set  should  come  ahead  of  the  foregoing 


1 

'^ 

m 

', 

E 

1 

- 1 

I 

j 
1 

'"[^^^m 

M 

m  -. 

^^^^//axiei^ 

* 

^M^mJMt 

HHI 

1^ 

The   vacuum   gap   type   of  lightning   arrester   is    widely    employed 

for    receiving    stations    only.      It    is    automatic    in    its    operation, 

being   always   ready  for   action,   no  matter   whether   the  receiving 

set  is  being  used  or  not. 


150  RADIO   FOR   EVERYBODY 

data  on  the  operation  of  the  simple  receiving  sets.  But 
as  a  matter  of  fact  one  need  pay  little  attention  to  the 
installation  of  the  simple  sets,  for  the  reason  that  their 
simplicity  limits  their  efficiency,  so  that  the  finer  details 
of  installation  hardly  apply  to  them.  When  it  comes  to 
elaborate  vacuum  tube  receiving  sets,  it  may  be  well  to 
give  a  little  thought  to  the  installation  for  the  purpose 
of  obtaining  the  utmost  efficiency. 

To  begin  with,  the  receiving  apparatus  should  be  so 
placed  as  to  permit  of  the  shortest  possible  leads  from  the 
receiver  to  the  point  where  the  antenna  lead-in  enters  the 
building.  Sufficient  space  should  be  provided  between 
the  instrument  and  the  edge  of  the  desk  or  table  to  allow 
the  operator  to  rest  his  forearm  when  adjusting  the  con- 
trols. Right  here  we  can  draw  a  comparison  with  the 
simpler  sets,  which  have  a  single  knob  or  perhaps  two 
knobs  on  top  of  the  case  or  on  the  side,  the  adjustment 
of  which  does  not  have  to  be  so  delicate  as  to  call  for  the 
resting  of  the  forearm.  In  the  case  of  elaborate  vacuum 
tube  apparatus,  however,  the  turning  of  a  knob  a  hair's 
breadth  may  make  for  all  the  difference  between  distorted 
music  or  talk,  or  perfect  reception. 

The  antenna  lead  from  the  lightning  switch  should  pass 
through  the  wall  or  window  within  a  porcelain  tube  or 
special  lead-in  insulator.  We  have  already  read  of  the 
board  which  can  be  placed  in  the  window  frame  so  that 
the  window  may  be  raised  or  lowered  without  interfering 
with  the  lead-in  passing  through  the  board  placed  at  the 
top  or  the  bottom  of  the  window  frame.  If  the  lead-in 
is  not  insulated  itself — heavily  insulated  wire  is  generally 
employed  for  this  purpose — then  it  should  be  supported 
away  from  the  walls  by  means  of  small  wall  insulators. 
The  ground  connection  lead  does  not  require  any  special 
insulation ;  ordinary  No.  14  rubber  covered  copper  wire  is 
well  adapted  to  this  purpose. 

From  Bed  Springs  to  Fire  Escapes  and  to  Loops 

There  are  times  when  one  cannot  install  the  usual  type 
of  antenna  for  receiving  purposes.    In  such  an  event  one 


RADIO  FOR  EVERYBODY 


151 


j^ 


Too    much    pain»    cannot    be   taken    vrith    the    ground    connection. 

The  ground  may  seem  simple  enough — and  it  is;  but  one   should 

use    a    good    ground    clamp    whenever    possible,    and    connect    it 

with  the  cold  water  pipe  for  best  results,  as   shown  here. 

need  not  give  up  the  idea  of  radio,  for  almost  anything 
will  serve  for  an  antenna  especially  when  receiving  from 
nearby  stations.  Excellent  results  may  be  obtained  with 
a  piece  of  wire  about  40  feet  long,  just  strung  back  and 


152 


RADIO   FOR  EVERYBODY 


forth  in  a  room  or  placed  behind  the  picture  moulding 
so  as  to  be  out  of  sight.  We  know,  of  a  man  who 
uses  an  antenna  for  receiving  from  the  Newark  broad- 
casting station  at  a  distance  of  250  miles,  and,  on  oc- 
casion, from  Pittsburgh,  some  650  miles  away.  The  same 
man  receives  the  signals  of  Nauen,  Bordeaux,  and  other 
European  high  power  stations  with  the  same  antenna. 

The  usual  fire  escapes  found  in 

the   city  make  excellent  antennas. 

However,  care  must  be  taken  in 


Simple  vacuum  tube  hook-up  for  use  with  a  loop  antenna. 
Note  that  VC  is  a  variable  condenser;  GL — grid  leak;  V — 
variometer  acting  as  the  "feed  back"  inductance;  T — tele- 
phone receivers;  B — *'B"  or  plate  battery;  FC — fixed  con- 
denser; K — rheostat  for  filament  current;  A — filament  battery. 
This  arrangement  will  operate  over  short  distances.  For 
greater   range   a  radio   frequency   amplifier  must    be   used 

scraping  the  paint  ofif  clean  in  order  to  make  a  good  con- 
nection with  the  metal.  Sometimes  a  gas  pipe  makes  an 
excellent  antenna,  while  the  water  pipe  is  used  for  the 
ground.  If  nothing  better  presents  itself,  a  metal  bed- 
stead or  bed  spring  serves  as  an  antenna,  with  good  re- 
sults.    Indeed,   the  problem   of  the  antenna  need  never 


RADIO  FOR  EVERYBODY  153 

trouble  the  radio  devotee,  for  the  reason  that  with  the 
sensitive  receiving  equipment  of  today  most  anything  will 
serve  as  an  antenna  when  working  over  short  distances. 

Then  we  have  the  loop,  which  takes  the  place  of  antenna 
and  ground  connection.  The  loop  is  connected  in  the 
same  way  as  would  be  the  secondary  of  a  vario-coupler  or 
loose-cO'Upler.  A  condenser  is  placed  across  the  loop 
terminals  so  as  to  vary  the  wave  length.  A  typical  loop 
hookup  is  given  in  the  accompanying  wiring  diagram, 
which,  it  will  be  noted,  makes  use  of  a  plate  variometer 
as  the  feed-back  in  order  to  obtain  regenerative  action. 
A  loop  outfit  of  this  kind  gives  good  results  over  reason- 
able distances,  although  it  does  not  cover  the  same  dis- 
tance as  would  the  same  equipment  when  used  with  a 
good  antenna.  However,  during  the  summer  months 
when  there  are  many  lightning  storms  and  when  static  is 
-at  its  very  worst,  the  loop  presents  an  interesting  means 
of  reception.  To  begin  with,  the  loop  is  safe  from  light- 
ning even  at  the  height  of  a  lightning  storm,  since  it 
can  be  used  indoors.  Furthermore,  the  loop  does  not 
pick  up  static  as  does  the  usual  antenna,  for  the  reason 
that  it  -does  not  make  use  of  a  ground  connection.  But 
it  is  well  to  remember  that  a  loop  intercepts  but  a  small 
portion  of  the  usual  energy  intercepted  by  a  good  antenna. 
Therefore,  for  best  results  a  radio  frequency  amplifier, 
such  as  described  in  the  chapter  on  amplifiers,  should  be 
employed  in  order  to  build  up  the  wave  energy  intercepted. 
The  loop  is  a  directional  receiver — it  receives  best  when 
pointed  end  on  towards  the  transmitter.  Many  inter- 
esting experiments  can  be  performed  with  a  loop. 

Elaborate  receiving  sets  presuppose  the  use  of  the 
vacuum  tube  detector,  for  no  really  efficient  radio  reception 
at  considerable  distances  can  be  obtained  without  this  form 
of  detector.  With  the  introduction  of  the  vacuum  tube, 
however,  the  operation  of  a  receiving  set  becomes  a  trifle 
more  complicated  than  with  the  crystal  detector,  for  while 
the  latter  does  not  give  forth  sounds  of  its  own  and  is 
virtually  silent  except  for  the  wireless  telegraph  and  radio 
telephone  waves,  the  vacuum  tube  creates  plenty  of  noises 


154  RADIO   FOR  EVERYBODY 

of  its  own  in  addition  to  the  desired  signals  and  telephone 
messages  and  music.  A  person  passing  from  a  simple 
crystal  set  to  a  vacuum  tube  set  may  be  disappointed  at 
first,  because  the  vacuum  tube  makes  so  much  noise  and 
has  to  be  tamed  occasionally,  so  to  speak,  in  order  to 
subdue  it,  especially  when  using  the  utmost  regenerative 
action.  But  when  the  vacuum  tube  is  once  adjusted  prop- 
erly, the  clarity  of  the  received  messages  or  music,  together 
with  the  strength  of  such  messages  or  music,  is  so  far 
ahead  of  the  crystal  detector  as  to  make  a  comparison  a 
sheer  waste  of  time. 

Vacuum  tubes  should  not  be  put  in  place  until  it  has 
been  ascertained  that  all  battery  connections  have  been 
correctly  made.  This  will  avoid  the  accidental  destruction 
of  the  tubes.  The  tubes,  which  cost  upwards  of  $5.00 
each,  may  be  burnt  out  just  as  any  electric  lamp  can  be 
burnt  out  by  applying  excessive  voltage  on  the  filament. 
There  are  on  the  market  little  fuses  which  fit  on  the  con- 
necting pins  of  any  vacuum  tube,  and  it  may  be  the  part  of 
good  judgment  to  provide  one's  vacuum  tubes  with  these 
little  fuses  as  a  measure  of  protection.  At  any  rate,  if  all 
battery  connections  are  checked  over  and  found  to  be 
correct,  it  will  avoid  the  accidental  destruction  of  the 
tubes  whether  fuses  are  provided  or  not. 

The  filament  lighting  battery,  which  is  generally  a 
storage  battery,  may  be  placed  on  the  floor  directly  be- 
neath the  apparatus  and  the  wires  connecting  this  battery 
with  the  apparatus  should  be  at  least  No.  14  B.  &  S.  copper 
wire,  properly  insulated.  Dry  battery,  consisting  of  four 
cells,  may  be  used  with  a  single  standard  detector  tube, 
but  it  is  expensive  practice   and   not   very   satisfactory. 

The  condition  of  a  storage  battery  may  be  tested  by 
means  of  a  hydrometer  or  a  voltmeter.  The  hydrometer 
is  an  instrument  which  measures  the  specific  gravity  of 
the  storage  battery  liquid  or  electrolyte,  to  give  it  the 
technical  name.  The  cap  or  plug  of  each  cell  of  storage 
battery  is  removed,  and  the  hydrometer  tube  is  inserted 
in  each  cell.    Squeezing  the  rubber  bulb  of  the  hydrometer^ 


RADIO   FOR   EVERYBODY 


155 


and  then  releasing  it,  causes  the  electrolyte  to  rise  in  the 
glass  tube  of  the  hydrometer.    The  specific  gravity  can  be 


Xarge  loop  antenna  employed  for  the  reception  of  trans-Atlantic 

messages   by   a   New   York   newspaper.      The    loop    is   mounted    so 

that    it    can    be    orientated    or    pointed    towards    the    transmitting 

station. 


156  RADIO   FOR   EVERYBODY 

readily  determined,  and  the  relative  charge  of  the  cell  ob- 
tained in  this  manner,  by  means  of  the  bob  or  float. 

One  popular  form  of  hydrometer  now  on  the  market 
has  three  colored  balls  in  the  glass  tube,  instead  of  the 
usual  bob  with  buckshot,  which  may  be  a  little  confusing 
to  the  layman.  If  all  three  balls  of  this  new  hydrometer 
stay  up  when  the  electrolyte  is  introduced,  the  battery 
is  fully  charged.  If  the  white  ball  goes  down  or  sinks,  the 
battery  is  all  right.  If  the  green  goes  down,  the  charge 
is  lean.  If  the  red  goes  down,  the  charge  is  dead.  This 
hydrometer  affords  a  simple  test  for  any  storage  battery. 

When   using  a  voltmeter,   it  is  necessary  to  have  an 


The   construction    of   a   **B"   battery,    showing    the    separate    cells, 

the   waterproof    partitions,    the    special   insulation,    the    terminals, 

and  the  method  of  sealing:  the  entire  battery. 

instrument  especially  intended  for  the  purpose,  which 
measures  from  0  to  3  volts,  or  0  to  5  volts.  The  fully 
charged  cell  registers  2.2  volts.  When  the  voltage  drops 
to  1.8  volts  per  cell,  the  battery  should  be  recharged.  To 
allow  the  cell  to  drop  below  1.7  volts  is  bad  practice,  for 
it  hastens  the  wear  and  tear  on  the  battery. 

Storage  batteries  are  rated  in  ampere  hours.  Generally 
speaking,  a  20-ampere-hour  battery  will  furnish  a  current 
of  1  ampere  for  20  hours,  5  amperes  for  four  hours,  and 


RADIO   FOR  EVERYBODY  157 

so  on.  If  a  vacuum  tube  detector  alone  is  being  used, 
then  a  20-ampere-hour  capacity  is  sufficient.  If  ampli- 
fiers are  employed,  a  60-ampere-hour  storage  battery 
should  be  used.  Vacuum  tubes  of  the  standard  type  re- 
quire about  1  ampere  each,  so  that  a  60-ampere-hour  bat- 
tery should  operate  a  receiving  set  of  detector  and  two- 
step  amplifier  for  about  20  hours,  after  which  the  battery 
must  be  recharged. 

Storage  batteries  may  be  recharged  by  means  of  a  simple 
home  recharger,  or  can  be  sent  to  a  nearby  garage  or 
battery  service  station.  The  home  recharging  sets  are 
designed  for  direct  or  alternating  currents.  The  latter 
class  are  of  two  general  types,  namely,  the  vibrating  reed 
type  and  the  vacuum  tube  rectifying  type.  The  former 
has  a  vibrating  reed  which  rectifies  the  alternating  current 
and  steps  it  down  to  a  suitable  charging  current.  The 
vacuum  tube  rectifying  type  has  a  special  vacuum  tube 
which  rectifies  the  current.  A  transformer  steps  down 
the  current.  The  author  has  used  a  vibrating  reed  re- 
charger  with  excellent  results,  and  at  a  cost  of  but  a  few 
cents  for  each  charge.  In  fact,  in  the  long  run  a  recharg- 
ing set  pays  for  itself  many  times  over,  since  the  regular 
price  of  recharging  a  battery  is  50  cents  to  $1.00  in  most 
service  stations,  while  the  cost  with  a  home  recharging 
set  is  a  matter  of  10  to  20  cents,  depending  on  the  size  of 
the  battery  and  the  length  of  charge. 

The  plate  batteries,  which  are  the  high  voltage  batteries, 
will  be  most  accessible  if  placed  directly  back  of  the 
receiver  so  that  the  wires  can  be  readily  brought  to  the 
proper  binding  posts  of  the  receiver  and  amplifier  units. 
Of  late  a  number  of  B  storage  batteries  have  appeared 
on  the  market.  It  is  claimed  that  the  storage  battery  type 
is  more  economical  in  the  long  run  than  the  dry  battery, 
and  that  it  furnishes  a  more  uniform  and  less  noisy  cur- 
rent, which  is  an  important  consideration  in  vacuum  tube 
work.  These  batteries  run  about  22  or  24  volts  per  unit, 
and  two  units  can  be  used  for  amplifier  operation.  They 
can  be  readily  recharged,  since  their  ampere  hour  capacity 
is  2  or  less. 


158 


RADIO   FOR  EVERYBODY 


x\ll  receiving  sets  and  amplifier  units  are  provided  with 
jacks  or  binding  posts  for  one  pair  of  telephone  receivers. 
If  the  jack  is  used — the  jack  is  simply  a  metal  hole  or 
socket  in  which  fits  a  plug  fastened  on  to  the  cords  of  a 
telephone  receiver — only  one  telephone  receiver  or  head 
set  can  be  used  at  a  time.  However,  there  has  recently 
appeared  on  the  market  a  multiple  plug,  which  is  inserted 
in  the  jack  in  the  usual  manner  and  which  provides  two 


Vibrating  type  of  rectifier  and  stepdown  transformer  outfit 
for  recharging  storage  batteries  on  the  usual  alternating  cur- 
rent supply  line.  The  vibrating  reed,  which  appears  under  the 
handle,  rectifies  both  sides  of  the  alternating  current  so  that 
direct  current  is  obtained.  The  volume  of  direct  current  is 
indicated  by   the   ammeter. 

holes  or  jacks  for  two  head  sets  or  for  a  head  set  and  a 
loud-speaker,  each  instrument  being  provided  with  the 
proper  plug.  Furthermore,  there  is  also  available  a  mul- 
tiple jack  which  may  be  mounted  on  an  instrument  or  on 
a  table  near  the  instrument.  The  multiple  jack  presents 
three  jacks  all  connected  in  series  and  so  constructed  that 
one,  two  or  three  plugs  can  be  inserted.     As  each  plug 


RADIO   FOR  EVERYBODY  159 

is  inserted,  it  connects  itself  automatically  in  series  with 
the  circuit,  while  the  unused  jacks  are  short-circuited  so 
that  the  circuit  will  remain  closed  except  for  the  jack  or 
jacks  being  used.  The  use  of  these  devices  is  to  be  recom- 
mended where  more  than  one  person  is  to  listen  in.  Of 
course,  where  binding  posts  are  used  for  the  telephone 
connection,  two  pairs  of  telephone  receivers  can  be  clamped 
under  the  binding  posts. 

When  the  telephone  receivers  are  connected  directly 
with  a  vacuum  tube  detector,  they  may  be  arranged  in 
parallel,  but  when  they  are  used  with  a  one  or  two-step 
amplifier,  they  should  be  arranged  in  series  because  of  the 
high  voltage  used.  In  the  latter  case  they  are  arranged 
with  one  tip  of  each  telephone  set  going  to  one  of  the 
binding  posts,  while  the  two  remaining  tips  of  the  tele- 
phone sets  are  connected  together,  thus  putting  the  sets 
in  series.  The  use  of  the  multiple  jack  or  multiple  plug 
simplifies  this  matter  and  makes  positive  and  noiseless 
connections. 

A  Few  Pointers  on   Operating  the  Receiving  Set 

With  the  fifty-seven  varieties  or  more  of  receiving  sets 
now  on  the  market,  it  would  be  impossible  to  give  precise 
directions  on  the  operation  of  each  set.  However,  the 
vacuum  tube  receiving  sets  fall  into  a  few  general  classes, 
so  that  broad  instructions  on  each  class  are  certain  to  fit 
every  individual  case  with  due  allowance  made  for  the 
peculiarities  of  each  particular  set. 

The  simplest  vacuum  tube  set  is  of  the  single  circuit 
type,  in  which  no  loose-coupler  or  vario-coupler  is  used. 
Furthermore,  no  regenerative  action  is  employed,  which' 
greatly  simplifies  the  operation  but  also  makes  the  set 
less  sensitive  than  it  might  be.  Such  a  set  makes  use  of 
a  tuning  coil  or  variometer,  and  perhaps  a  condenser.  The 
inductance  may  be  fixed,  in  the  form  of  a  compact  in- 
ductance unit,  with  a  condenser  in  series  or  in  parallel 
to  vary  the  wave  length.  However  that  may  be,  the  ad- 
justment of  wave  length  comes  down  to  the  one  or  two 
components,  and  is  soon  restored  in  each  case. 


160  RADIO   FOR  EVERYBODY 

The  operation  of  the  vacuum  tube  requires  a  little  care. 
The  filament  rheostat  must  be  varied  until  the  best  signals 
are  obtained,  after  tuning  them  in  to  the  utmost  strength. 
Generally  the  signals  are  loudest  and  clearest  when  the 
filament  rheostat  is  moved  up  to  a  point  just  before  the 
hissing  sound  is  heard  in  the  telephone  receivers.  With 
most  vacuum  tubes,  the  plate  voltage  is  critical  for  best 
results,  so  that  the  B  battery  should  be  varied  in  order 
to  obtain  the  loudest  and  clearest  signals.  Either  a  B 
battery  of  the  variable  voltage  type  can  be  employed,  or  a 
rheostat  can  be  placed  in  series  with  the  battery  and  the 
plate  circuit.  For  the  very  best  results,  a  potentiometer 
should  be  used  with  the  B  battery  for  the  most  accurate 
adjustments.  The  potentiometer  is  a  resistance  placed 
across  the  source  of  energy,  while  hooking  up  to  one  side 
and  using  a  sliding  contact  to  take  current  off  the  resist- 
ance at  any  point,  thus  making  for  very  delicate  control 
as  compared  with  the  simple  series  resistance  of  the  usual 
rheostat. 

The  use  of  the  regenerative  arrangement  complicates 
the  operation  of  a  set  not  a  Httle  but  it  also  makes  for 
louder  signals  than  could  ever  be  obtained  with  a  simple 
circuit.  Regeneration  is  obtained  either  by  means  of  a 
tickler  coil  or  by  a  grid  variometer,  as  a  general  thing. 
Take  the  case  of  the  tickler  coil,  which  controls  the 
amount  of  regenerative  or  feed-back  action.  First  the 
detector  tube  is  adjusted  until  it  is  as  near  silent  as  pos- 
sible, yet  responds  to  the  spark  signals.  This  is  generally 
before  the  point  where  the  tube  becomes  noisy,  although 
at  times  the  temperamental  tube  works  best  when  the 
rheostat  has  been  moved  past  the  noisy  point  and  into 
another  zone  of  relative  silence.  Then  the  tuning  handle 
or  handles  are  adjusted  so  as  to  bring  in  the  desired  sig- 
nals or  telephone  messages.  Furthermore,  by  means  of 
the  tickler  handle,  the  quality  of  the  reception  can  be 
improved  if  necessary.  If  too  much  tickler  action  is  used, 
the  signals  or  the  radio-phone  are  apt  to  be  mushy  and 
distorted  because  of  excessive  regeneration.     Finally,  the 


RADIO   FOR   EVERYBODY  161 

signals  or  radio-phone  are  refined  by  turning  the  vernier 
adjustment,  if  the  set  is  provided  with  such  a  device. 
The  vernier  is  simply  an  auxiliary  tuner  which  deals  with 
much  finer  variations  than  the  main  tuner.  It  is  neces- 
sary in  the  best  types  of  receivers,  because  regenerative 
circuits  are  extremely  sensitive  and  sharply  tuned  for  the 
best  results. 

Generally,  when  using  the  regenerative  method  of  recep- 
tion, a  radio-phone  station  denotes  its  presence  by  a 
whistling  sound  as  the  tuner  is  varied.  By  moving  the 
tuner  back  and  forth  over  the  entire  range  of  wave 
lengths,  whistling  sounds  may  be  detected  at  certain  points. 
Then  the  tuner  is  finally  adjusted  so  as  to  get  in  between 
these  whistling  sounds,  where  there  is  a  silent  zone.  It 
is  in  this  zone  that  the  radio-phone  music  or  talk  is  heard. 
At  other  times  these  whistling  sounds  are  due  to  contin- 
uous wave  or  undamped  wave  transmitters,  which,  like 
the  radio-phone,  make  use  of  the  same  kind  of  waves  and 
therefore  have  the  same  characteristics. 

Once  adjusted,  a  regenerative  receiving  set  will  main- 
tain its  adjustment  fairly  well.  Occasionally,  the  vernier 
or  the  tuner  may  have  to  be  readjusted,  especially  if  the 
character  of  the  music,  if  one  is  listening  in  to  a  radio- 
phone concert,  is  changed  materially.  The  filament 
rheostat  may  also  be  altered  at  times  to  improve  the 
strength  or  the  clarity  of  the  music. 

When  it  comes  to  two-  and  three-circuit  receiving  sets, 
the  tuning  requires  more  care,  otherwise  the  operation  is 
the  same.  Again  the  tickler  adjustment,  starting  at  zero, 
is  gradually  increased  until  a  position  is  reached  just 
below  the  oscillating  point.  The  oscillating  condition  is 
indicated  by  a  soft  hissing  sound  in  the  telephone.  The 
final  adjustments  are  maae  with  the  vernier  or  verniers. 
Sometimes  it  may  be  found  necessary  to  adjust  the  tuner 
and  the  tickler  at  the  same  time  in  order  to  maintain  the 
proportion  necessary  to  keep  the  receiver  on  the  verge 
of  the  oscillating  condition,  which  is  the  most  sensitive 
one.  The  adjustment  of  the  coupler  will  also  be  found 
most  important,  more  so  when  one  is  endeavoring  to  cut 


162  RADIO   FOR  EVERYBODY 

down  interference  to  a  minimum.  After  all,  the  main 
advantage  of  the  two-  and  three-circuit  receivers,  over  the 
single  circuit  regenerative  receivers,  is  that  they  provide 
real  means  of  eliminating  troublesome  interference. 

(NCOMINC 


vwwvww 


LOCAX. 


BEAT 
CURRENT 


4AAaaAMaa/VVw' 


H^OOULATEO 
PLATE  CURRet^r 


APPROXIMATE 

nUEPHONC 

CURRENT 


0-$ 

How  CW  waves  are  detected,  with  an  undamped  receiving- 
arrangement.  The  CW  wave  is  shown  to  represent  the  in- 
coming signals.  The  local  circuit,  employing  a  vacuum 
tube,  is  made  to  oscillate,  producing  its  own  wave  or  local 
current,  which  differs  but  slightly  from  the  frequency  of 
the  incoming  signals.  This  slight  difference  sets  up  a 
*'beat  current."  This  beat  current,  in  turn,  modulates  the 
plate  current  as  shown,  which  is  pulsating  direct  current, 
having  been  rectified  from  the  alternating  beat  current. 
Finally  the  telephones  slur  the  modulated  plate  current 
variations   into    the   large    pulsations    indicated. 

Spark  Signals  and  C  W  Signals 

The  reception  and  amplification  of  spark  signals  will 
be  most  satisfactory  when  the  regenerative  action  is  con- 
trolled to  a  degree  which  will  produce  maximum  ampli- 
fication without  causing  an  oscillating  condition  in  the 


RADIO   FOR   EVERYBODY  163 

circuits.  When  the  oscillating  condition  is  reached,  which 
is  indicated  by  hissing  noise,  the  tone  of  the  spark  signal 
will  be  destroyed  and  reception  through  interference  will 
become  virtually  impossible.  The  tone  of  a  spark  trans- 
mitter, which  means  a  damped  wave  transmitter,  may  be 
altered  when  adjusting  the  receiver  from  the  plain  de- 
tector action  to  the  oscillating  condition.  That  accounts 
for  the  fact  why  a  transmitter,  which  is  heard  as  a  series 
of  flute-like  dots  and  dashes  one  moment,  becomes  a  mushy 
but  extremely  loud  series  of  dots  and  dashes  the  next. 
The  flute-Hke  sounds  are  the  real  sound  values  of  the 
sparks,  while  the  mushy  sounds  are  the  false  sound  values 
given  to  them  by  the  oscillating  action  of  the  detector. 

What  are  known  as  continuous  wave  signals,  including 
the  interrupted  continuous  waves  and  the  modulated  con- 
tinuous waves,  all  of  which  are  explained  in  the  chapter 
further  on  dealing  with  continuous  wave  transmission,  as 
wx'll  as  the  radio-phone,  may  be  received  in  like  manner, 
but  a  special  condition  may  be  obtained  by  allowing  oscil- 
lations to  take  place  in  the  receiver,  producing  the  exact 
frequency  of  the  incoming  wave  length.  This  is  known  as 
the  ''zero  beat"  method  and  in  this  condition  amplification 
is  greatly  increased  due  to  the  augmented  feed-back  of 
energy  from  the  plate  to  the  grid  circuit.  It  is  only  pos- 
sible to  make  use  of  this  method  while  the  incoming  fre- 
quency remains  constant,  and  its  successful  application 
requires  considerable  skill. 

In  the  reception  of  continuous  waves  the  plate  circuit 
feed-back  or  tickler  action  is  to  be  increased  to  a  point 
where  oscillations  are  constantly  taking  place  and  this 
condition  must  be  maintained  throughout  the  entire  tuning 
operations. 

The  most  successful  means  for  reducing  spark  inter- 
ference while  receiving  modulated  continuous  wave  sig- 
nals, including  radio-phone,  is  the  use  of  the  zero  beat 
method  described  above.  This  will  cause  the  spark  signal 
to  become  distorted  and  suppressed  while  greatly  increas- 
ing the  amplification  of  the  desired  signal.  As  the  oscil- 
lating   condition   is    a    prerequisite    in    the    reception    of 


164  RADIO   FOR  EVERYBODY 

continuous  wave  signals,  it  follows  that  spark  signals  are 
more  readily  suppressed  than  are  the  modulated  contin- 
uous wave  signals.  Where  the  carrier  wave  length  of  the 
modulated  continuous  wave  signal  and  the  wave  length 
of  the  undesired  signal  are  almost  identical,  it  may  be 
possible  to  suppress  the  undesired  signal  by  changing  the 
frequency  of  the  desired  signal  to  the  point  where  the 
carrier  wave  frequency  of  the  modulated  continuous  wave 
signal  is  beyond  audibility.  The  coupler  adjustment  also 
makes  for  additional  freedom  from  spark  interference. 
The  elimination  of  continuous  wave  signals  while  receiving 
spark  signals  is  easily  accomplished  by  reducing  the  plate 
variometer  or  tickler  dial  settings  until  the  oscillations 
cease,  unless  the  continuous  wave  station  is  very  powerful 
and  located  nearby. 

From  Radio-Phone  to  Dots  and  Dashes 

Sooner  or  later,  and  better  sooner  than  later,  the  radio 
enthusiast  turns  to  dots  and  dashes  because,  after  all.  the 
radio  telegraph  still  dominates  the  air  as  far  as  the  volume 
of  traffic  is  concerned.  While  the  music  and  the  radio- 
phone talks  may  be  most  interesting  to  the  laity,  the  fact 
remains  that  many  things  of  great  importance  are  being 
missed  if  one  does>  not  understand  the  telegraph  code. 

Formerly,  the  Morse  telegraph  code  was  largely  em- 
ployed in  radio  telegraph  work  in  this  country.  At  that 
time  the  Marconi  land  stations  and  ship  installations  used 
the  Continental  code,  which  is  the  present  code,  while  the 
other  radio  organizations  as  well  as  the  Government  and 
amateur  stations  used  the  Morse  code,  which  is  the  code 
used  on  our  telegraph  lines.  However,  in  order  to  have 
a  uniform  code  with  the  rest  of  the  world,  the  Continental 
<:ode  was  finally  adopted  as  the  standard  radio  code.  This 
code  differs  from  the  former  Morse  code  in  the  fact  that 
it  has  no  spaces  between  the  letters  themselves.  In  the 
Morse  code,  for  instance,  the  letter  C  is  represented  by 
dot  dot  space  dot.  The  letter  R  is  just  the  reverse,  namely, 
dot  space  dot  dot.  Now,  since  there  are  spaces  between 
the  letters  themselves,  it  stands  to  reason  that  the  space 


Form  778  U 

Department  of  Commerce 

BUREAU  OF  NAVIGATION 

RADIO  SERVICE 

INTERNATIONAL  MORSE  CODE  AND  CONVENTIONAL  SIGNALS 

TO  BE  USED  FOR  ALL  GENERAL  PUBLIC  SERVICE  RADIO  COMMUNICATION 

1.  A  dash  is  eiqual  to  three  dots. 

2.  The  space  between  parts  of  the  same  letter  is  equal  to  one  dot. 

3.  The  space  between  two  letters  is  equal  to  three  dots. 

4.  The  space  between  two  words  is  equal  to  five  dots. 

A  .  _ 
B  _  .  .  . 
C , 

Period.... -. 

Semicolon . . . 

D  _  .  . 
E  . 

Comma —  .  —  .  — 

F , 

G :, 

11 

Colon 

Interrogation . .  . 

K 

FTrlfimaHnll  pnlllt                                                                             

ApoKtrophp                                                        .  _.                     . 

L . 

M 

Hyphen —  ....  — 

Bar  Indlcatlnir  fraction. —  .  .  _  . 

P  . . 

Parenthesis - . .  . . 

n .  _ . 

T_ 

AV  . 

Underline 

Double  dash 

Z .  . 

Attention  call  to  precede  every  trans- 

General  Inquiry  call —  .  —  . .  — 

A  (German)  .  .  

i  or  A  (Spanish-Scandinavian) 

From  (de) —  .  .      , 

CH  (German-Spanish) 

Invitation  to  transmit  (go  ahead) 

t  (French)  .  .  _  .  . 

5i  (Spanish) . 

0  (German) . 

I'  (German)  .  . 

AVamlnp — ^hlpfi  power                                         .  .  .  •      ,  — . 

Question   (please  repeat   after )— 

Walt . 

Break  (Bk.)  (double  dash) _  .  .  .  _ 

1  . 

2  .  . .^ 

Understand —  . 

3 

4  .  .  .  . 

Error • 

ppr^lrpd  (0.  K.)                                           . . 

5 

6  _  .  .  .  , 

Position  report  (to  precede  all  position 

messages) —     .  —  . 

8 ,  , 

End  of  each  message  (cross) . . 

9 _, 

Transmission    finished    (end    of    work) 

(eoncluslon  of  correspondence). . 

11—6860 

Chart    of   the    Continental    radio    code    as    now    employed    in    all    radio 
communicatioji. 


166  RADIO    FOR   EVERYBODY 

between  the  dots  and  dashes  forming  a  single  letter  must 
be  shorter  than  those  between  letters,  and  it  is  this  fea- 
ture w^hich  makes  the  code  more  complicated  and  more 
liable  to  error  than  the  Continental  code,  which  has  no 
spaces  within  the  letters  themselves. 

The  Continental  code  may  be  readily  mastered  with  a 
Httle  patience.  The  best  method  to  proceed  in  learning  the 
telegraph  language  is  to  learn  the  code  letters  not  so 
much  by  remembering  the  dot  and  dash  combinations 
^s  by  learning  the  sounds.  In  other  words,  when  an 
operator  listens  to  a  telegraph  message  he  does  not  notice 
the  dot  and  dash  combinations  of  each  letter  and  then 
translate  these  combinations  into  the  proper  letter  or 
numeral.  Instead,  he  catches  the  certain  sound  or  com- 
bination of  each  letter  or  numeral,  and  automatically  his 
trained  mind  reads  off  the  message  in  letters.  The 
■trained  operator  never  thinks  of  the  letters  in  dots  and 
dashes,  just  as  the  reader,  in  reading  this  line  of  type, 
does  not  notice  the  letters  in  each  word  but  recognizes 
words  as  complete  units  by  their  general  appearance. 
In  writing,  the  same  is  true.  The  rapid  writer  does 
not  think  of  each  letter  as  he  writes;  his  words  are  his 
units,  and  he  writes  as  he  thinks. 

Therefore,  the  code  must  be  learned  by  means  of  some 
instrument  which  simulates  radio  dots  and  dashes.  For 
this  purpose  a  simple  buzzer  operated  by  a  battery  and 
a  telegraph  key,  may  be  used.  Again,  one  can  purchase  a 
regular  practice  set,  which  has  buzzer  and  key  com- 
bined in  one  unit.  A  very  ingenious  little  practice  set  is 
shown  in  the  accompanying  illustration,  which  contains 
a  battery,  buzzer,  telegraph  key,  and  a  lamp  for  visual 
signals. 

The  first  step,  once  the  practice  set  is  at  hand,  is  to 
learn  the  code  letter  by  letter.  The  code  is  given  in  the 
chart  on  page  165.  Note  that  A  is  a  dot  and  a  dash 
This  is  translated  into  a  short  snappy  push  on  the  tele- 
graph key  followed  by  a  longer  push.  The  key  should  be 
held  with  the  index  and  middle  fingers  of  the  right  hand 
resting  lightly  but  firmly  on   top  of  the  knob,  with  the 


RADIO   FOR   EVERYBODY 


167 


thumb  in  light  contact  at  the  side  or  beneath  the  rim  of  the 
key  knob.  All  characters  should  be  made  by  wrist  motion, 
with  the  elbow  stationary,  and  all  muscles  of  the  arm 
and  fingers  should  remain  perfectly  flexible.  One  of  the 
most  difficult  things  for  the  beginner  to  learn  is  proper 
wrist  motion,  which  is  so  essential  to  good  transmitting. 
The  beginner  should  never  start  with  the  key  knob  close  to 
the  table,  due  to  the  fact  that  this  will  interfere  with 
the  forearm  and  free  wrist  movement.  Transmitting  in- 
volves a  downward  pressure  on  the  key  of  short  or  long 
duration,  it  being  unnecessary  to  do  any  elevating  of  the 

key  as  this  is  pro- 
vided for  by  the 
spring  compression 
under  the  key. 

The  beginner 
should  first  learn  to 
recognize  the  letters 
of  the  Continental  or 
International  code  in- 
stantly when  heard, 
without  conscious  ef- 
fort. In  order  to  ac- 
quire this  knowledge 
he  should  start  to 
send  at  a  slow  rate  of 
speed,  remembering  that  a  dash  is  equivalent  in  duration 
of  time  to  that  taken  for  making  three  dots.  When  opera- 
ting the  key,  listen  to  the  sound  produced  by  the  buzzer,  or, 
if  the  practice  set  has  a  visual  indicator  such  as  a  lamp, 
watch  the  flash  produced  by  the  blinker,  as  it  is  called.  In 
a  surprisingly  short  time  smoothness  and  speed  in  both 
sending  and  receiving  will  be  developed.  In  some  prac- 
tice sets  a  head  receiver  is  worn  so  that  the  buzzes  are 
heard  in  the  same  manner  as  though  they  were  received 
from  a  radio  telegraph  transmitter. 

Taking  the  telegraph  code,   the  beginner  should  start 
with  the  first  four  letters,  mastering  them  in  turn.     Thus, 


Buzzer  practice  set  employed  in 
learning  the  radio  code.  This  little 
set  is  also  provided  witli  a  small 
lamp  which  gives  visual  code  signals 
when   desired. 


168  RADIO   FOR  EVERYBODY 

the  beginner  will  note  by  studying  the  code  chart  that 
dah  de  dah  de — and  not  dash  dot  dash  dot — is  C,  in- 
stantly, and  that  dah  de  de  de  is  B.  In  other  words,  he 
learns  what  sounds  represent  each  letter,  and  he  does  not 
stop  to  figure  how  many  dots  and  dashes  he  has  heard. 
It  is  left  to  the  mind  to  perform  two  functions  for  each 
letter,  namely,  to  think  of  the  symbol  and  then  the  letter. 
It  will  be  found  that  as  the  code  is  mastered,  the  letters 
will  form  in  the  brain  automatically,  and  when  this  stage 
is  reached  the  speed  can  be  greatly  increased. 

After  mastering  the  first  four  letters,  the  beginner  goes 
on  to  the  next  four.  With  these  mastered,  he  repeats 
all  the  letters  from  the  beginning  again,  and  then  passes 
on  to  the  next  four,  and  so  on.  It  may  require  several 
evenings  to  memorize  all  the  letters  and  numerals,  and 
£nally  one  can  go  on  to  the  various  punctuation  marks 
-and  other  characters.  To  recognize  the  symbols  instantly, 
even  when  they  are  sent  at  slow  speed,  takes  much 
longer,  of  course.    Sending  is  much  simpler  than  receiving. 

With  all  the  symbols  memorized,  the  beginner  should 
sit  down  by  the  hour  and  translate  newspaper  articles  or 
magazine  articles  or  any  other  "copy"  into  the  Continental 
code,  using  the  practice  set.  In  this  manner  he  trains  his 
ear  to  the  various  sounds,  and  after  all  the  ma:stering  of 
the  code  is  just  that,  nothing  more. 

The  next  step  is  one  which  presents  two  alternatives : 
Either  the  beginner  can  get  in  touch  with  some  other  be- 
ginner and  spend  some  time  each  week  transmitting  mes- 
sages back  and  forth  to  each  other  by  means  of  a  buzzer 
practice  set,  or  the  beginner  can  listen  in  on  his  receiving 
set  to  the  amateur  transmitting  stations,  endeavoring  to 
pick  up  letters  here  and  there.  The  second  method  is  not 
apt  to  produce  immediate  results,  for  the  reason  that 
,much  of  the  traffic  is  entirely  too  fast  for  the  beginner. 
However,  certain  radio  telegraph  broadcasting  stations 
have  the  beginner  very  much  in  mind  these  days,  and 
transmit  at  a  very  slow  speed  in  order  to  furnish  prac- 
tice   for   the  beginner.      There    are   automatic   machines 


170  RADIO  FOR  EVERYBODY 

which  send  messages  at  any  desired  speed  for  training  the 
beginner.     This  is  an  excellent  self-instructor. 

One  method  of  learning  the  code  is  to  attend  a  radio 
school.  The  schools,  thanks  to  their  wide  experience,  have 
perfected  methods  of  training  beginners  which  produce 
early  results.  But  in  the  main  one  can  teach  one's  self 
if  sufficient  patience  is  exhibited.  Listening  to  radio 
telegraph  stations  and  attempting  to  jot  down  on  paper 
as  many  letters  as  are  recognized  finally  results  in  copy- 
ing more  and  more  letters  and  words  until  perfection  is 
attained. 

Aside  from  the  telegraph  code,  there  are  certain  abbre- 
viations that  have  been  inaugurated  by  the  International 
Radio  Convention.  The  list  of  these  abbrevations  is  pre- 
sented on  the  facing  page,  and  while  it  may  not  neces- 
sarily be  memorizd,  it  is  well  to  remember  the  more  im- 
portant ones. 

When  and  Where  A  Radio  License  is  Necessary 

Having  mastered  the  code  and  become  a  radio  operator 
of  more  or  less  ability,  a  person  can  consider  a  trans- 
mitting set.  Otherwise  a  transmitting  set  is  out  of  the 
question,  unless  one  has  a  licensed  operator  to  run  it. 
The  owner  of  an  amateur  transmitting  station  must  ob- 
tain a  station  license  before  it  can  be  operated  if  the 
signals  radiated  therefrom  can  be  heard  in  another  state, 
and  also  if  such  a  station  is  of  sufficient  power  to  cause 
interference  with  neighboring  licensed  stations  in  the 
receipt  of  signals  from  transmitting  stations  outside  the 
state,  which  means  that  virtually  all  transmitters  must  be 
licensed.  These  regulations  cover  the  operation  of  radio 
telephone  stations  as  well  as  radio  telegraph  stations. 

Station  licenses  can  be  issued  only  to  citizens  of  the 
United  States,  its  territories  and  dependencies. 

Transmitting  stations  must  be  operated  under  the  super- 
vision of  a  person  holding  an  operator's  license,  and  the 
party  in  whose  name  the  station  is  licensed  is  responsible 
for  its  activities. 


Form  T72  a. 


Department  of  Commerce 

BUREAU  OF  NAVIGATION 

RADIO  SERVICE 


INTERNATIONAL  RADIOTELEGRAPHIC  CONVENTION 
LIST  OF  ABBREVIATIONS  TO  BE  USED  IN  RADIO  COMMUNICATION 


ANSWER  OR  NOTICB 


PRB 

QR\ 
QRB 
QUC 
QRD 
QRP 
QRO 
QRH 
QR4 
QRK 
QRL 


QSP 


•QSV 

QSW 
QSX 
QSY 

QSZ 


QTE 
QTF 


Do  yon  wish  to  communicate  by  means  of  the 
International  Signal  Code! 

What  ship  or  coast  station  la  that? 

What  Is  yonr  distance! 

What  Is  yonr  true  bcarln;! 

Where  are  yon  bound  for? 

Where  are  yon  bound  fromt 

What  line  <lo  yon  bclonp  tot 

What  Is  your  wave  length  In  meterst 

How  many  words  have  yon  to  send! 

How  do  yon  receive  meJ 

Are  yoa  receiving  badlyJ     Shall  I  send  201 . . 

for  adjustment?   

Are  you  being  Interfered  wlthl 

Are  the  atmospherics  strong? 

Shall  I  increase  power? 

Shall  I  decrease  power? 

Shall  I  send  faster? 

Shall  I  send  slower? , 

Shall  I  stop  sending? 

Have  yon  anything  for  mc: 

Are  yon  ready? 

Are  you  busy? 


Shall  I  standby? 

When  will  be  my  turn? 

Are  my  signals  weak? 

Are  my  signals  strong? 

ris  my  tone  bad? 

[Is  my  spark  bad? 

Is  my  spacing  bad? 

What  Is  yonr  time? 

Is  transmission  to  be  In  altenuite  order  or  la 
series? 


MTiat  rate  shall  I  collect  for 

Is  the  last  radiogram  canceled  .  „ 

Did  yon  get  my  receipt! 

What  Is  yonr  true  course? 

Are  yon  in  communication  with  land? , 

Are  yon  In  communication  with  ftny  ship  or 

station  (or:  with )? 

Shall  I  Inform tbzt  yon  are  calling 

hlmt 

Is calllB];  met 

Will  yon  forward  the  radloframt 

Have  you  received  the  general  call? 

Please  call  me  when  you  have  finished  (or: 

at o'clock)? 

Is  public  correspondence  being  handled? 


Shall  I  increase  my  spark  frequency? . 
Shall  I  decrease  my  spark  frequency? . 
Shall  I  send  on  a  wave  length  of.. 
meters? 


What  Is  my  true  bearing?  . 
What  Is  my  position? 


I  wish  to  commanlcate  by  means  of  the 
International  Signal  Code. 

This  is 

My  distance  is 

My  true  bearing  Is degrees. 

I  am  bonnd  for 

I  am  bound  from 

I  belong  to  the Line. 

My  wave  length  is meters. 

I  have. . . . words  to  send. 

I  am  receiving  well. 

I  am  receiving  badly.    Please  send  20. 

for  adJDStment. 
I  am  being  Interfered  with. 
Atmospherics  are  very  strong. 
Increase  power. 
Decrease  power. 
Send  faster. 
Send  slower. 
Stop  sending. 
I  have  nothing  for  yon. 
I  am  ready.    All  right  now. 

I  am  busy  (or:  I  am  busy  with ). 

Please  do  not  interfere. 
Standby.    I  will  call  yon  when  required. 

Yonr  turn  will  be  No 

Yonr  signals  are  weak. 
Yonr  signals  are  strong. 
The  tone  Is  bad. 
The  spark  Is  bad. 
Yonr  spacing  is  bad. 

My  time  Is 

Transmission  will  be  In  alternate  order. 

Transmission  will  be  In  series  of  5  message*. 
Transmission  will  be  in  series  of  10  messagt-. 

Collect 

The  last  radiogram  Is  canceled. 
Please  acknowledge. 

My  true  course  is degrees. 

I  am  not  in  communication  with  land. 

I    am    In    communication    with , 

(through ). 

Inform. that  I  am  calling  him. 

You  are  being  called  by 

I  win  forward  the  radiogram. 
General  call  to  all  stations. 
Will  call  when  I  have  finished. 

Public  correspondence  Is  being  handled. 

Pleas*  do  not  interfere. 
Increase  yonr  spark  frequency. 
Decrease  your  spark  frequency. 
Let  ns  change  to  the  wave  length  of 

meters. 
Send  each  word  twice.    I  have  difflcnity  In 

receiving  you. 
Sepeat  the  last  radiogram. 

Your  true  I>eajing  Is degrees  from 

Yonr  position  is  —  latitude longitude. 


*  Public  correspondence  ia  any  radio  work,  offidal  or  private,  handled  oa  com- 
mercial wave  lengths. 

_  When  an  abbreviation  is  followed  by  a  mark  of  interrogation,  it  refers  to  the  ques- 
tion indicated  for  that  abbreviation.  ii— «86o 


List   of  abbreviations   now   employed   in   radio   communication  for   the 
purpose  of  saving  time  and  trouble. 


172  RADIO   FOR   EVERYBODY 

The  Government  licenses  granted  for  amateur  stations 
are  divided  into  three  classes  as  follows : 

Special  Amateur  Stations,  known  as  the  "Z"  class  of 
stations,  are  usually  permitted  to  transmit  on  wave  lengths 
up  to  approximately  375  meters. 

General  Amateur  Stations,  which  are  permitted  to  use 
a  power  input  of  1  kilowatt  and  which  cannot  use  a 
wave  length  in  excess  of  200  meters. 

Experimental  Stations,  known  as  the  "X"  class,  and 
school  and  university  radio  stations,  known  as  the  '*Y" 
class,  are  usually  allowed  greater  power  and  also  allowed 
the  use  of  longer  wave  lengths  at  the  discretion  of  the 
Department  of  Commerce,  which  has  charge  of  the  grant- 
ing of  licenses  and  the  enforcement  of  the  radio  laws. 

All  stations  are  required  to  use  the  minimum  amount 
of  power  necessary  to  carry  on  successful  communication. 
This  means  that  while  an  amateuf  station  is  permitted  to 
use,  when  circumstances  require,  an  input  of  1  kilowatt, 
this  input  should  be  reduced  or  other  means  provided  for 
lowering  the  antenna  energy  when  communicating  with 
nearby  stations  in  which  case  full  power  is  not  required. 

Malicious  or  wilful  interference  on  the  part  of  any  radio 
station  or  the  transmission  of  any  false  or  fraudulent  dis- 
tress signal  or  call  is  prohibited.  Severe  penalties  are 
provided  for  violation  of  these  provisions. 

Special  amateur  stations  may  be  Hcensed  at  the  dis- 
cretion of  the  Secretary  of  Commerce  to  use  a  longer 
wave  length  and  higher  power  than  general  amateur  sta- 
tions. Applicants  for  special  amateur  station  licenses 
must  have  had  two  years'  experience  in  actual  radio  com- 
munication. A  special  license  will  then  be  granted  by 
the  Secretary  of  Commerce  only  if  some  substantial 
benefit  to  the  science  of  radio  communication  or  to  com- 
merce seems  probable.  Special  amateur  stations  located 
,on  or  near  the  sea  coast  must  be  operated  by  a  person 
holding  a  commercial  license.  Amateur  station  licenses 
are  issued  to  clubs  if  they  are  incorporated,  or  if  any 
member  holding  an  amateur  operator's  license  will  accept 
the  responsibility  for  the  operation  of  the  apparatus. 


174  RADIO   FOR   EVERYBODY 

Applications  for  operator's  and  station  licenses  of  all 
classes  should  be  addressed  to  the  Radio  Inspector  of  the 
district  in  which  the  applicant  or  station  is  located,  or, 
if  this  is  not  known,  to  the  Bureau  of  Navigation,  Depart- 
ment of  Commerce,  Washington,  D.  C.  The  accompany- 
ing map  indicates  the  territory  covered  by  each  radio 
district. 

Each  district  has  a  Radio  Inspector,  w^hose  address  is 
given  below : 

First  District Boston,  Mass. 

Second  District New  York  City 

Third  District Baltimore,  Md. 

Fourth  District Norfolk,  Va. 

Fifth  District New  Orleans,  La. 

Sixth  District San  Francisco,  Calif. 

Seventh  District   Seattle,  Wash. 

Eighth  District Detroit,  Mich. 

Ninth   District    Chicago,    111. 

Once  more,  let  it  be  clearly  understood  that  no  Hcense 
is  required  for  a  receiving  set  only  or  for  the  operator 
of  a  receiving  set.  However,  all  persons  are  required 
by  law  to  maintain  secrecy  in  regard  to  any  messages 
which  may  be  overheard.  This  is  a  blanket  law,  of  course, 
intended  to  safeguard  the  interests  of  those  transmitting 
and  receiving  private  dispatches  and  special  press  reports, 
and  does  not  apply  to  broadcasted  telegraph  and  telephone 
service. 

Persons  who  wish  to  operate  a  transmitting  set  must 
apply  to  the  radio  inspector  of  their  district  for  the  neces- 
sary form  and,  at  an  appointed  time,  undergo  an  exam- 
ination which  covers  their  proficiency  in  receiving  and 
sending  telegraph  messages,  as  well  as  in  the  theory  and 
practice  of  radio.  Operator's  licenses  are  of  the  amateur 
and  commercial  grade,  depending  on  the  proficiency  of  the 
person  examined.  There  is  no  fee  or  charge  for  either 
an  operator's  or  a  station  license. 

Every  person  engaged  in  any  form  of  radio  communi- 
cation should  have  a  copy  of  a  pamphlet,  ''Radio  Com- 
munication Laws  of  the  United  States,"   which  can  be 


£.W 


176  RADIO   FOR  EVERYBODY 

secured  by  sending  fifteen  cents  (not  in  stamps)  to  the 
Superintendent  of  Documents,  Government  Printing 
Office,  Washington,  D.  C. 

The  laws  regulating  the  operation  of  private  radio 
stations  in  Canada  are  different  in  several  respects  from 
those  in  force  in  the  United  States.  For  instance,  a 
station  which  is  used  only  for  receiving  must  have  a 
station  license.  For  authoritative  information,  inquiry 
should  be  rnade  of  the  Deputy  Minister  of  the  Naval 
Service,  Ottawa,  Ontario. 

Call  Letters  and  What  They  Mean 

All  radio  transmitters  have  call  letters.  Just  as  auto- 
mobiles carry  license  plates  with  the  State  and  a  number 
plainly  marked  on  them,  so  do  all  radio  transmitting  sta- 
tions use  calL  letters  consisting  of  two  or  three  or  four 
letters  and  numerals.  If  one  station  wishes  to  call  an- 
other station,  it  calls  by  means  of  the  call  letters  of 
the  desired  station.  The  Government  assigns  call  letters 
at  the  time  the  station  license  is  granted.  Every  radio 
amateur  should  have  a  copy  of  the  pamphlets  ''Amateur 
Radio  Stations  of  the  United  States,"  and  "Commercial 
and  Government  Radio  Stations  of  the  United  States." 
The  price  of  each  of  the  pamphlets  is  fifteen  cents,  and 
orders  should  be  sent  to  the  Superintendent  of  Docu- 
ments. These  pamphlets  contain  lists  of  the  amateur,  and 
commercial  and  Government  stations  in  the  United  States, 
and  of  the  call  letters  assigned  to  the  stations.  A  new 
edition  of  each  pamphlet  is  published  on  June  30  of  each 
year.  A  monthly  publication  called  the  ''Radio  Service 
Bulletin"  is  issued  which  contains  information  regarding 
changes  in  the  radio  regulations  and  traffic. 


Chapter  VI. 

MAKING  BIG  SOUNDS  OUT  OF  LITTLE 

ONES,  OR  THE  GENTLE  ART 

OF  AxMPLIFYING 


MUCH  of  the  present  success  of  radio  depends  on  the 
amphfier  apparatus  now  in  use.  The  ampHfier  is 
the  instrument  which  makes  possible  the  magnifying  of 
Aveak  signals  or  sounds  in  an  electrical  circuit.  An  incom- 
ing radio-phone  wave  may  be  so  weak  that  the  sounds 
cannot  be  heard  in  the  telephone  receiver,  yet  throw  in 
one  step  or  stage  of  amplification  and  immediately  the 
sounds  are  loud  and  clear.  The  music  or  the  talk  as- 
sumes a  depth  and  roundness  that  has  been  lacking  when 
receiving  with  the  ordinary  detector  circuit.  Throw  in 
another  step  of  amplification  or  two  steps  in  all,  and  the 
sounds  are  so  loud  that  they  can  be  heard  when  the 
telephone  receivers  are  laid  on  the  table.  Or,  a  loud- 
speaking  device  may  be  hooked  up  and  immediately  the 
sounds  are  heard  throughout  the  room  without  the  aid  of 
the  telephone  receivers. 

The  amplifier  has  served  to  increase  the  range  of  all 
transmitters  to  an  unbelievable  extent.  Thus  with  a 
given  transmitter  in  the  old  days  of  crystal  detectors,  the 
usual  range  might  have  been  say  100  miles.  Today,  thanks 
to  the  regenerative  receiving  circuit  already  described, 
which  amplifies  the  signals  considerably,  and  also  thanks 
to  a  two-step  amplifier,  the  same  transmitter  may  operate 
a  thousand  miles  with  ease.  Not  that  the  transmitter  is 
any    the   more   powerful   or  more   efficient    than   it   was 


178  RADIO   FOR  EVERYBODY 

formerly,  but  the  receiving  set,  because  of  the  regenerative 
arrangement  and  the  amphfier,  responds  when  the  waves 
are  that  much  more  attenuated  or  weakened. 

From  Transatlantic  Radio  to  Transcontinental 
Telephone 

The  amphfier  is  responsible  for  many  of  our  recent 
achievements.  For  instance,  the  recent  spanning  of  the 
Atlantic  by  twenty-nine  amateur  transmitters,  usmg  one 
kilowatt  or  less  and  a  wave  length  below  200  meters, 
would  have  been  impossible  were  it  not  for  the  highly 
efficient  receiving  equipment  and  amplifier  employed  by 
the  American  observer  stationed  in  Scotland  for  the 
purpose  of  picking  up  the  weak  signals.  An  ordinary  set 
would  not  respond  to  such  signals,  and  the  transmitters 
would  be  said,  under  such  circumstances,  to  be  incapable 
of  spanning  the  3,000  miles  or  more  of  space  between 
America  and  Scotland. 

Yet  with  the  proper  receiving  set  and  super-amplifier, 
the  transmitters  were  found  to  span  the  intervening  space 
with  a  varying  degree  of  success.  Which  only  serves  to 
prove  once  more  that  no  matter  how  weak  the  trans- 
mitter may  be,  its  waves  are  propagated  through  space 
and  keep  on  going  farther  and  farther  away  with  virtually 
no  end.  It  may  seem  fantastic  to  believe  that  the  waves 
from  a  little  amateur  transmitter  when  once  started  keep 
on  going  through  space  for  years  and  years,  until  they 
may  reach  the  moon  and  the  distant  planets ;  but  such 
must  be  the  case.  The  whole  problem  is  one  of  having 
a  receiving  set  sufficiently  sensitive  to  respond  to  the 
attenuated  waves,  and  then  an  amplifier  -^^hich  can  build 
up  the  signals  to  audibility. 

The  amplifier  principle  is  used  in  telephone  work.  The 
trans-continental  telephone  would  not  be  the  success 
which  it  is  were  it  not  for  the  vacuum  tubes  now  em- 
ployed as  amplifiers  or  repeaters.  After  going  through 
many  hundred  miles  of  wire  and  becoming  attenuated  as  a 
result,  the  weakened  telephonic  currents  are  passed 
througfh  vacuum  tubes  in  order  to  impress  their  charac- 
teristics on  other  circuits,  which  in  turn  have  fresh  and 


RADIO   FOR   EVERYBODY 


179 


powerful  currents  ready  for  another  jump^  of  several 
hundred  miles.  These  currents,  in  due  course,  become  at- 
tenuated  in  their  turn,  and  again  resort  is  had  to  vacuum 
tube  devices.  The  vacuum  tube  has  proved  to  be  the 
most  reliable  form  of  telephonic  relay  or  repeater  ever 


DETECTOR     AND     AMPLIFIER    FILAMENT 
\                                   RHEOSTATS. 

! 

j 

DETECTOR- 
SWITCH 

TUNINO 
PANEL 

J 

Combination  tuner  and  detector-amplifier  set  nuade  up   of  two 
units  mounted  one  above  the  other  as  shown.     This  comprises 
an  excellent  receiving  set,  with  detector  and  two-stage  ampli- 
fier  completely    self-contained. 

developed,    working   with    virtually    no    distortion    when 
properly  designed  and  handled. 

In  the  previous  chapter  we  had  something  to  say  re- 
garding the  action  of  the  vacuum  tube.  We  learned  of 
the  flow  of  electrons  or  ions  from  the  hot  filament,  and 
how  this  flow  of  electrons  or  ions  formed  a  one-way 
bridge  for  the  B  battery  current  connected  with  the  tele- 


Y 


vO 


H'I'I'I'I'I'I'I'I*- 


\siMjmj 


r-|l|l  1  1  1  l|l  1 

CO 

T 

\<^/ 

' UUUMiL 

HiNi|«|i|i|i|i|»— ^^^"^^^^"^^ 

cQ  H 


5  fl  S^ 


aj  rt  35 
-OS  fl 


11 


*  T  2  -  i 

SI  fci  .5  5  3 


«  si 


«  9 


S  •"«      - 

as  OS  a 

S  I  -S-^ 

4>0  «   ©-§ 

.2  5      g  i> 
5S  2tt  *• 

fc,  «5  4,  !8  © 

III  A 


RADIO   FOR  EVERYBODY  181 

phones.  And  the  grid,  as  we  learned,  is  the  control  for 
the  traffic  over  this  one-way  bridge.  In  the  case  of  the 
amplifier  tube,  the  grid  is  again  employed  as  the  control 
Instead  of  using  a  pair  of  telephone  receivers  in  the 
plate  circuit  of  the  receiving  set,  the  two  leads  or  "out- 
put" terminals  are  brought  to  the  amplifier  apparatus,  as 
shown  in  the  accompanying  diagram.  The  first  step  is 
to  pass  the  receiving  circuit  current  through  the  primary 
of  a  special  amplifying  transformer.  Such  transformers 
are  available  in  many  different  styles  but  all  serve  the 
same  general  purpose.  They  are  sometimes  called  inter- 
valve  transformers.  The  secondary  of  the  transformer 
is  brought  to  the  grid  and  to  the  filament  of  the  amplifier 
tube,  as  shown.  The  plate  circuit  of  the  amplifier  tube 
contains  a  B  battery  of  higher  voltage  than  the  detector 
B  battery,  and  the  telephone  receivers.  However,  if  an- 
other stage  or  step  of  amplification  is  desired,  then  the 
plate  current  from  the  first  tube  is  brought  to  the  primary 
of  a  second  amplifying  transformer,  and  the  secondary 
is  connected  with  the  grid  and  filament  as  before.  This 
second  amplifier  bulb  has  a  B  battery  and  a  pair  of  tele- 
phone receivers  or  the  loud-speaking  device,  as  the  case 
may  be.  A  third  step  may  be  added  in  the  same  manner. 
Three  steps  or  stages  of  amplification  are  considered  the 
limit  in  actual  practice,  for  the  reason  that  beyond  that 
point  tlxe  adjustment  of  the  circuits  becomes  too  difficult 
for  satisfactory  work.  Please  note  that  the  same  fila- 
ment and  B  battery  may  be  used  for  the  detector  and  the 
amplifier  tubes,  but  for  the  sake  of  simplicity  most  of  our 
diagrams  show  separate  batteries  being  used  for  each 
tube. 

Whereas  the  amplifier  tubes  and  detector  tubes  may 
look  alike,  they  are  quite  different  as  far  as  the  electrical 
characteristics  are  concerned.  Amplifier  tubes  are  not 
critical  in  adjustment  when  compared  with  detector  tubes 
and  they  will  operate  successfully  on  plate  voltages  of  40 
to  80  volts.  Where  a  detector  and  two  stages  of  ampli- 
fication are  used,  three  22^  volt  units  may  be  connected 


182  RADIO   FOR   EVERYBODY 


■(ENT    RriC05T.MS  iNTdRVA^vt    T»!<MiFoS>«F  RS  Tl'Bt      S.OCKET5 


Simple  mounting  for  a  two-stage  amplifier,  comprising  the  fila- 
ment rheostats,  the  intervalve   or  amplifying  transformers,  and 
the  tube  sockets. 

in  series  and  connections  to  the  receiver  made  in  a  manner 
which  permits  the  use  of  the  full  voltage  on  the  amplifier 
tubes  while  a  variable  portion  of  the  same  battery  is 
used  for  the  detector  tube,  say  anywhere  from  16  to  22 
volts.  Where  extremely  loud  signals  are  desired  the 
plate  voltage  may  be  100  or  over ;  and  while  such  high 
voltage  will  not  damage  the  amplifier,  it  will  increase 
tube  noises,  and  is  therefore  not  desirable  when  receiving 
signals  with  the  telephone  head  set.  No  more  than  45 
volts  is  required  even  with  several  pairs  O'f  head  phones. 
An  amplifier  tube  which  requires  a  critical  plate  voltage 
or  filament  current  adjustment  wili  not  give  consistently 
satisfactory  results  as  an  amplifier.  Tubes  of  this  charac- 
ter will  generally  be  found  useful  as  detectors. 

Audio  or   Radio   Frequency — Which? 

The  amplifying  arrangements  described  so  far,  and  for 
that  matter  the  greater  part  of  the  amplifying  apparatus 


RADIO   FOR   EVERYBODY 


183 


now  available  and  in  regular  use,  is  known  as  the  audio- 
frequency type.  It  is  called  the  audio  frecjuency  type 
for  the  reason  that  it  is  handling  currents  of  frequencies 
well  within  the  audible  range.  There  is  another  type  of 
amplifier  known  as  the  radio-frequency  type,  which,  up 
till  the  present  time,  has  been  rarely  used.  However,  at 
this  writing  the  radio  frequency  type  is  rapidly  coming 
into  general  use  for  long-range  reception,  as  well  as  in 
connection  with  loop  antennae  and  diminutive  antennae  of 
all  kinds.  In  the  case  of  audio-frequency  amplification,  the 
amplifying  is  done  after  the  signals  have  been  passed 
through  the  detector  and  rectified  so  as  to  produce  audio- 
frequency currents,  while  with  the  radio  frequency  ampli- 


ORiD    !_EAK 
AND   CONDENSE^ 


HOLES    foR  i^^°"^    FREQUENCYJ 

CONNECTIONS 


Components  of  a  combination  radio  frequency  amplifier,  vacuum 

tube  detector,  and  audio  frequency  amplifier,  mounted  in  a  neat 

steel  cabinet. 


184  RADIO   FOR  EVERYBODY 

fier  the  waves  are  amplified   before  they  are  passed   to 
the  detector. 

The  advantage  of  the  radio-frequency  ampHfier  lies  in 
the  fact  that  it  amplifies  only  the  wave  and  not  the 
many  little  irregularities  and  imperfections  which  exist  in. 
the  usual  receiver  and  amplifier  equipments.  Further- 
more, most  detectors  have  a  critical  point  at  which  they 


FILAMENT    RHEOSTATS 

WiNOOW    \FOR   AMPLIFIER  TUBE.3 


"^^"-^^-^    FOR    DETECTOR     OR 
AMPLiFiER    CO.MNECTfON 


Two-stage  audio  frequency  amplifier,  with  filament  rheostat 
handles,  switch  handle  for  connecting:  the  detector  alone,  or 
one  stage  or  two  stages  of  amplification  into  the  circuit,  as 
well  as  the  input,  output,  and  filament  current  binding  posts 
mounted    on   the   front   paneL 

begin  operating.  Signals  which  come  in  weaker  than  the 
critical  point  of  the  detector  make  no  impression  on  the 
detector,  and  are  therefore  lost  entirely.  No  matter  how 
many  steps  of  audio-frequency  amplification  may  be  piled 
up  behind  the  detector,   the  signal  which  has   failed  to- 


RADIO   FOR   EVERYBODY 


185 


actuate  the  detector  will  certainly  not  be  heard.  With 
radio- frequency  amplification,  on  the  other  hand,  there  is 
virtually  no  critical  point,  and  even  the  weakest  signal  is 
built  up  to  the  desired  degree  before  it  is  passed  on  to 
the  detector,  there  to  be  rectified  to  audio-frequency  cur- 
rent, which,  if  desired,  can  be  passed  on  through  one  or 
more  stages  of  audio-frequency  amplification  in  order  to 
build  up  the  signal  strength. 

In  extreme  long-distance  work,  it  is  not  uncommon  to 


^0-60  VOLTS     b 

I 
6  VOLTS  a 

Resistance  type  of  radio-frequency  amplifier.  Tlie  set  of 
wires  b  are  for  tlie  plate  battery  current,  with  the  polarity 
indicated,  while  the  a  set  indicates  the  filament  battery  current. 
The  wire  marked  1  is  the  grid  wire  from  the  tuner.  R  are 
the  filament  rheostats;  Rl,  2  are  resistances;  Am  are  ampli- 
fier tubes;  D  is  the  detector  tube;  FC — fixed  condenser;  T — 
telephones;   VC — variable  condenser. 


find  two  stages  of  radio-frequency  amplification,  followed 
by  a  detector  and  two  stages  of  audio-frequency  amplifi- 
cation. 

When  using  a  loop  antenna,  it  is  usually  necessary  to 
employ  radio-frequency  amplification  unless  one  is  near 
the  desired  transmitter.  The  radio-frequency  ampHfier 
builds  up  the  wave  energy  before  passing  it  on  to  the 
detector,  and  in  that  manner  enables  one  to  hear  signals 
which  would  not  affect  the  detector  otherwise.  After 
all  is  said  and  done,  it  is  really  the  radio-frequency  ampli- 
fier which  makes  for  extreme  sensitiveness  in  the  receiv- 


186  RADIO   FOR  EVERYBODY 

ing  set,  and  enables  almost  urtbelievable  distances  to  be 
spanned,  while  it  is  the  audio-frequency  amplifier  which 
makes  for  loud  signals  and  for  the  successful  operation 
of  loud-speaking  devices. 

The  simplest  type  of  radio-frequency  amplifier  is 
known  as  the  resistance-coupled  type,  and  is  shown  in  the 
wirins^  diagram  on  page  185.  In  this  arrangement  the 
amplifying  transformers  are  replaced  by  suitable  resis- 
tances and  condensers,  the  amplified  energy  bemg  passed 
from  one  circuit  to  the  other  by  means  of  the  resistance 
coupling.  This  method  is  preferable  in  many  instances 
because  of  its  simplicity  and  because  of  the  fact  that 
the  radio  or  the  audio  frequency  can  be  amplified  at  will. 

If  the  grid  condenser  is  eliminated  on  some  of  the  tubes 
in  a  multi-stage  amplifier,  as  shown  in  the  diagram  on 
page  185,  then  the  incoming  radio  frequency  is  amplified 
before  it  is  rectified,  and  after  it  is  rectified  by  going 
through  the  detector  tube  it  is  then  amplified  again  at 
audio  frequency  in  order  to  obtain  volume  of  sound. 
Amplifying  at  radio  frequencies,  although  it  is  rather  diffi- 
cult to  do  so  at  times,  has  numerous  advantages  and  the 
experimenter  is  urged  to  try  amplifying  at  radio  fre- 
quencies wherever  possible  since  one  of  the  principal 
advantages  of  this  method  is  that  radio  frequencies  are 
inaudible  to  the  human  ear  and  the  amplifying  action 
is  therefore  carried  on  without  unpleasant  noises  to  the 
listening  operator. 

By  using  special  transformers  the  transformer  method 
■can  be  applied  to  radio  frequency  amplification,  reducing 
it  to  something  almost  as  simple  as  the  audio- frequency 
amplifier.  There  have  been  introduced  of  late  special 
radio  frequency  transformers  which  function  over  the 
wave  length  band  of  200  to  5,000  meters,  and  which  have 
been  designed  particularly  for  the  short  wave  band  of 
200  to  500  meters.  These  transformers  mark  a  real 
step  forward  in  the  art,  and  must  make  for  the  wide  appli- 
cation of  ithe  radio  frequency  method  of  ampHfying.  This 
method  of  amplification  doubles  and  triples  the  receiving 
ranges ;  it  makes  signals  audible  that  cannot  be  received 


o 


vjjkftjuu — i^ 


■oinnnnr 


03-=- 


X 


MSiSlSlSU 


r-nmnnrr\ 


} 


^ft 


188 


RADIO   FOR  EVERYBODY 


with  other  types  of  ampHfying  circuits ;  it  is  vastly 
superior  to  any  other  method  of  amphfying  telephone 
speech ;  it  eliminates  tube  noises ;  it  increases  selectivity ;  it 
increases  signal  audibility  at  each  stage  at  least  twenty 
times;  it  makes  possible  the  use  of  small  loops  or  frame 
antenna  to  receive  as  well  as  with  high  antennae ;  and  it 
gives  a  20-watt  amateur  radio  telephone  set  the  trans- 
mitting range  of  a  transmitter  of  several  times  the  power. 
Please  note  that  radio-frequency  amplification  can  be 
used  in  'Connection  with  any  existing  receiving  set,  even 
if  said  set  is  of  the  simplest  and  most  elementary  type. 


Another  radio-frequency  arrangement.  VCl — variable  con- 
denser in  aerial-ground  circuit;  LiC — loose-coupler  or  vario- 
coupler;  VC2 — variable  condenser  across  secondary;  Am — 
amplifier  tube;  Kl,  2,  3,  4 — rheostats;  PS — primary  and  sec- 
ondary of  intervalve  or  amplifying  transformer  T;  GL, — grid 
leak;  D — detector;  B — plate  battery;  A  1  and  2 — filament  bat- 
tery; rc — fixed  condenser;  T — telephones;  TICK — tickler 
coil;    G — ground. 

For  radio-frequency  amplification  builds  up  the  wave 
strength  before  it  is  passed  on  to  the  detector,  so  that 
in  every  sense  of  the  word  it  is  as  though  the  receiving 
set  were  moved  a  considerable  distance  towards  the  trans- 
mitter. Thus  a  crystal  detector  can  be  used  in  conjunction 
with  the  radio-frequency  amplifier,  for  after  the  wave 
strength  has  been  built  up  by  the  radio- frequency  ampli- 
fier, it  is  rectified  by  the  crystal  detector.  Then,  if  de- 
sired, the  rectified  current  from  the  crystal  detector  can 
be   amplified    by    means    of    audio-frequency    amplifiers. 


RADIO   FOR  EVERYBODY  189 

Sometimes  the  crystal  is  employed  in  this  manner,  for 
the  reason  that  it  is  silent  in  its  operation  and  is  not  apt 
to  introduce  noises  into  the  circuit. 

When  and  Where  to  Use  an  Amplifier 

Most  receiving  sets  are  complete  without  an  amplifier. 
In  other  words,  the  amplifier  is  something  apart  from  the 
regular  receiving  set ;  it  is  an  accessory ;  it  can  be  added 
at  any  time  to  the  usual  run  of  receiving  sets.  So  the 
question  arises  as  (to  when  and  where  an  amplifier  should 
be  employed. 

The  amplifier  of  the  audio-frequency  type,  which  is  the 
type  generally  used,  should  be  employed  when  loud  sig- 
nals  are  required.  Take  the  case  of  the  radio-phone 
service,  for  instance.  At  a  reasonable  distance  the  music 
and  talk  come  in  good  and  clear,  but  it  cannot  be  denied 
that  ithe  music  and  talk  are  generally  thin,  so  to  speak. 
The  music  or  the  talk  has  no  depth,  no  sense  of  realism. 
It  seems  to  be  in  one  plane,  just  like  the  motion  picture 
is  in  one  plane  when  viewed  on  the  ordinary  screen.  It 
lacks  the  depth  so  necessary  for  realism,  even  though  it 
may  be  quite  loud.  x\t  least  those  are  the  author's  obser- 
vations, as  well  as  those  of  many  persons  who  have 
listened  in  on  his  receiving  set.  However,  the  moment 
the  amplifier  is  used,  even  with  one  step,  there  is  introduced 
a  loudness  and  clarity,  as  well  as  depth,  which  make  for 
realism.  These  features  are  particularly  noticeable  in 
the  case  of  a  radio  chapel  service,  where  the  minister  may 
be  preaching  and  is  followed  by  the  choir.  Without 
amplifiers,  the  voice  of  the  minister  and  the  voices  of  the 
choir  are  on  the  same  plane,  but  with  the  amplifier  we 
obtain  a  sense  of  depth  and  the  entire  rendition  sounds 
as  though  it  were  in  a  large  church. 

So  the  amplifier,  then,  makes  for  better  results,  let  alone 
loudness.  Fortunately,  an  amplifier  is  not  such  an  elab- 
orate piece  of  mechanism.  It  consists  merely  of  a 
vacuum  tube  of  the  amplifier  model,  a  filament  rheostat,  a 
transformer,  and  the  necessary  batteries  and  connections. 
Like  the  vacuum  tube   detector,   it   requires  a   filament 


190 


RADIO   FOR   EVERYBODY 


battery  and  a  high-voltage  B  battery.  When  telephone 
head  sets  are  to  be  used,  only  45  volts  is  required  for  the 
B   battery.      In   that   case   two   B   battery  units   of   22/4 

volts  each  are  connected 
in  series,  and  a  tap  is 
taken  from  the  connec- 
tion between  the  units 
and  brought  to  the  de- 
tector in  order  that  the 
detector  will  not  have 
more  than  22^  volts, 
while  the  amplifier  will 
have  the  full  voltage. 
It  is  well  to  mention 
here  that  a  variable 
voltage    battery    should 


How  the  radio-frequency  amplifier  is  used  with  the  loop 
antenna  for  long  distance  reception.  VC  1 — variable  con- 
denser across  loop  terminals;  L.  1  and  Li  2 — inductance  coils; 
VC  2 — variable  condenser;  FC — fixed  condenser;  Am — amplifier 
tube ;  D — detector  tube ;  T — telephone  receivers ;  B — plate  bat- 
tery; A — filament  battery;  K  1  and  2 — filament  rheostat.  Note 
the    extra    resistance. 


RADIO   FOR  EVERYBODY  191 

be  used  for  the  detector,  since  a  good  detector  tube  has  a 
critical  voltage  adjustment  for  the  B  battery,  and  a  fixed 
voltage  battery  for  the  other  unit.  Some  battery  manu- 
facturers are  now  supplying  a  combination  B  battery  of 
45  volts,  with  part  of  the  battery  made  variable  so  as  to 
obtain  the  critical  B  battery  voltage  for  the  detector. 

Amplifier  units  can  be  purchased  at  a  reasonable  cost. 
Thev  come  in  one-stasre  and  two-stas^e  models,  and  in 
some  instances  a  three-stage  model  can  be  obtained,  al- 
though this  model  is  rare  for  the  reason  that  its  adjust- 
ment calls  for  considerable  skill  as  compared  with  the  one 
and  itwo-stage  models.  Then  again,  there  are  units  avail- 
able in  which  the  detector  is  included.  Thus  one  can 
obtain  a  detector  and  one-stage  model,  and  a  detector  and 
two-stage  amplifier  model. 

Fortunately,  the  same  storage  battery  is  employed  for 
the  detector  and  the  amplifier  tubes,  just  as  the  B  battery 
is  used  for  all  the  tubes  of  one  set.  This  simpHfies  the 
problem  and  makes   for  economy. 

A  so'ft  or  gassy  tube,  known  as  a  detector  tube,  should 
be  used  for  the  detector,  while  hard  or  highly  exhausted 
tubes  should  be  used  for  the  amplifiers.  However,  in 
some  sets  where  a  single  rheostat  may  be  employed  for 
the  detector  and  amplifier  tubes,  and  a  rigid  B  battery 
voltage  is  used  on  all  tubes,  it  is  sometimes  good  practice 
to  use  amplifier  tubes  throughout,  including  detection. 
This  is  not  the  most  efficient  practice,  but  it  makes  for 
simplicity,  since  amplifier  tubes  do  not  require  the  delicate 
manipulation  and  adjustment  that  are  called  for  with  soft 
or  gassy  tubes.  Of  course,  the  sensitiveness  w^hen  using 
amplifier  tubes  throughout  is  bound  to  be  greatly  reduced, 
for  it  is  the  delicate  adjustment  of  the  gassy  tube  which 
makes  it  so  highly  responsive  to  weak  signals. 

The  Question  of  Loud  Speakers 

Sooner  or  later  the  radio  enthusiast  wants  to  do  away 
with  head  'phones  in  order  that  the  radio-phone  service 


192 


RADIO   FOR  EVERYBODY 


may  be  used  for  danc- 
ing or  even  for  enter- 
taining a  roomful  of 
persons.  In  that  event 
some  form  of  loud- 
speaker must  be  used. 
The  simplest  form 
of  loud-speaker  is  one 
which  makes  use  of 
the  existing  receivers, 
without  extensive  al- 
terations of  the  re- 
ceiving and  amplify- 
ing arrangements. 
There  are  horns  avail- 
able which  may  be 
fitted  to  the  regular 
telephone  head  set. 
These  horns  are  pro- 
vided with  soft  rub- 
ber pieces  or  even 
with  clamps,  so  that  the  regular  head  set  may  be  held  in 
place  while  the  sounds  from  both  receivers  travel  up 
through  a  horn  and  are  amplified  so  as  to  be  audible  some 
distance  away.  These  devices  are  excellent  in  a  limited 
way,  and  their  main  attraction  is  the  fact  that  they  can 
be  used  without  alteration  of  any  kind. 

However,  where  something  of  a  more  ambitious  nature 
is  wanted,  it  becomes  necessary  to  use  special  loud- 
speakers. The  simplest  loud-speakers  are  those  which 
.make  use  of  a  single  telephone  receiver  of  the  same 
.general  type  as  those  used  with  head  bands,  as  well  as  a 
special  horn.  There  are  all  kinds  of  devices  of  this  gen- 
eral class,  ranging  from  horns  of  pressed  paper  or  wood 
pulp,  made  in  the  general  form  of  the  channels  of  the 
human  ear,  and  pressed  copper  reflectors,  as  well  as  horns 
of  a  more  conventional  design. 


liOud-speaker    attachment    that    fits    on 

the     tone-arm     of    any     phonograph     so 

that  the   usual  horn  of  the  phonograph 

is   used  to   amplify   the   sounds. 


RADIO   FOR  EVERYBODY 


193 


One  of  the  most  popular  forms  consists  of  a  specially 
designed  metal  horn  mechanically  attached  to  the  mechan- 
ism of  a  special  telephone  receiver,  in  which  the  stand- 
ard mica  diaphragm  has  been  replaced  by  a  strong  corru- 
gated metal  diaphragm  which  will  stand  practically  any 
amount  of  abuse  without  damage.  A  large  amount  of 
experimental  work  was  carried  on  by  radio  experts  before 
final  decision  was  made  on  the  horn  and  it  is  believed 
that  the  design  furnishes  as  fine  a  quality  of  reproduc- 
tion as  can  be  obtained  except  through  the  use  of  a 
very  elaborate  sound  chamber  such  as  is  found  in  high- 
priced  phonographs. 

The  loud-speaker  in  question,  which  is  shown  in  the 
accompanying  illustration,  will  work  satisfactorily   from 
a   two-stage   audio-frequency  amplifier   and,   using  good 
amplifying  tubes,  150-200  volts 
may  be  used  without  damage 
to   the   instrument.      By  good 
tubes   is   meant,    in   this   case, 
especially     ''hard'' 
tubes.     The  usual  am- 
p 1 i  f  y  i  n  g  tubes  are 
operated  on  45  volts, 
and   this    voltage    will 
produce  only  weak  re- 
sults   with    the    usual 
loud-speaker.    If  more 
B    battery    is    added, 
such  as  by  connecting 
a    third    and    even    a 
fourth   unit  to   the 
usual    B    battery,    the 
results  may  be  poorer 
with  the  regular  am- 
plifier tubes. 

Some  radio  workers 

use    the    5-watt    trans-  o^^    ^f  ^he    several    loud-speakers   now 

mittinc'"    tubes     as     am-  available    for    home    use.      This    model 

..^       ^     .  1  •    1  may    be    used    in    connection    with    any 

plmers,    m    which    case  two-stage  ampUfier. 


194  RADIO   FOR  EVERYBODY 

voltages  up  to  and  even  exceeding  100  volts  may  be  ap- 
plied. In  such  an  arrangement  it  is  well  to  try  the  5-watt 
tube  in  the  second  stage  of  amplification,  and  to  use  the 
regular  amplifier  tube  in  the  first  stage. 

One  form  of  loud-speaker  which  is  proving  very  popu- 
lar is  a  simple  telephone  receiver  of  special  construction 
which  may  be  attached  to  the  tone  arm  of  the  usual  phono- 
graph. In  this  manner  one  saves  the  cost  of  a  special 
horn,  and  at  .the  same  time  one  has  the  pleasure  of 
hearing  the  regular  phonograph  do  duty  as  a  radio  re- 
ceiver. The  results  with  such  an  arrangement  are  very 
good,  and  the  volume  may  be  made  extremely  great  by 
using  sufficient  voltage  on  the  telephone. 

Loud-speakers  require  plenty  of  voltage,  and  there  is 
no  getting  away  from  this  fact.  The  simple  devices  which 
take  the  the  regular  head  sets  or  single  receiver  operate 
ofif  the  regular  amplifier  output  without  changes  of  any 
kind ;  but  when  it  comes  to  filling  an  entire  room  with 
loud  music  or  talk,  the  problem  becomes  quite  complicated 
and  certainly  expensive. 

All  of  which  brings  us  up  to  the  problem  of  real  loud- 
speakers such  as  are  used  in  the  most  ambitious  kind  of 
radio  reception,  as  well  as  for  public  speaking  and  other 
work.  Hence  this  subject  is  worthy  of  treatment  at 
length,  including  a  ILttle  back  history.  Loud-speakers  of 
this  kind  are  known  as  electrodynamic  receivers. 

The  Early  Days  of  the  Electrodynamic  Receiver 

In  1911  two  inventors,  E.  S.  Pridham  and  P.  L.  Jen- 
sen, were  actively  affiliated  with  the  development  of  arc 
radio  transmission  and  reception  at  Napa,  California. 
During  the  course  of  work,  they  made  a  very  exhaustive 
study  of  various  methods  for  the  reception  of  rapid  radio 
signals.  Naturally  enough,  the  development  of  what  is 
known  as  the  string  galvanometer  was  carried  out,  and 
it  was  while  conducting  these  experiments  that  several 
new  and  improved  receiving  devices  were  built.  Among 
them  was  the  first  step  in  the  development  of  the  electro- 


RADIO   FOR  EVERYBODY 


195 


dynamic  receiver,  now  well  known  for  its  loud-speaking 
characteristics. 

This  early  type  was  built  along  the  lines  of  a  modern 
voltmeter,  with  a  revolving  coil  in  a  magnetic  field  at- 
tached by  lever  action  to  a  diaphragm.  This,  however, 
was  not  a  success  as  a  telephone  receiver,  and  while  it 


Special   power   amplifier,    used    in    connection    •with    extra    power- 
ful loud-speakers  such  as  are  employed  for  projecting  the  radio- 
phone  entertainment    in   a    large   hall.      This    amplifier   is   used   in 
addition  to  the  usual  amplifier  of  the  receiving   set. 


did  reproduce  the  voice  with  remarkable  distinctness,  it 
was  not  nearly  loud  enough,  or  even  as  loud  as  the  or- 
dinary electro'magnetic  type.  While  this  instrument  was 
not  important  in  itself  it  was  to  be  taken  into  considera- 
tion as  the  forerunner  of  the  practical  electrodynamic 
reproducer  of  today. 


196  RADIO   FOR  EVERYBODY 

After  many  experiments  with  the  revolving  coil,  the 
idea  was  definitely  given  up  and  a  new  line  of  experiments 
started.  The  next  instrument  developed  was  the  true 
electrodynamic  loud  speaker  or  receiver,  although  it  was 
not  known  at  that  time  that  it  had  loud-speaking  character- 
istics. Two  very  large  electromagnetic  structures  were 
made,  and  a  small  coil  of  fine  wire  wound  on  mica  about 
three  inches  long  by  one  inch  wide,  and  very  flat  and  thin, 
was  also  introduced.  This  coil  was  suspended  in  the  air 
gap  of  the  two  electromagnets,  rigidly  attached  to  a 
diaphragm.  The  coil  was  located  in  such  a  way  that  both 
the  three-inch  sides  of  the  flat  coil  were  in  a  strong  mag- 
netic field  of  the  proper  polarity  when  the  magnets  were 
energized.  Both  sides  of  the  diaphragm  were  enclosed 
and  ear  tubes  led  out,  one  side  for  each  ear.  The  total 
weight  of  the  receiver  was  about  sixty  pounds. 

At  once  it  was  found  that  this  new  receiver  had  different 
internal  characteristics  than  the  electromagnetic  type  of 
reproducer.  In  spite  of  the  great  weight  oif  movable 
parts  attached  to  diaphragm  alone,  about  two  ounces  for 
the  movable  coil,  it  was  found  that  the  new  instrument 
gave  better  speech  reproduction  from  weak  impulses  than 
the  ordinary  receiver.  Overtones  were  held,  consonants 
and  sibulent  sounds  were  reproduced  perfectly;  in  short, 
the  quality  of  the  speech  was  a  revelation.  But  in  spite 
of  the  fact  that  this  instrument  responded  to  impulses 
weaker  than  those  necessary  to  affect  t:he  electromagnetic 
type  of  receiver,  its  loud-speaking  qualities  were  still 
undiscovered ;  in  fact,  they  were  not  yet  developed  in  this 
particular  instrument. 

A  number  of  experiments  were  performed  with  this 
instrument  which  were  at  that  time  nothing  short  of  re- 
markable. The  two  inventors  realized  that  there  were 
great  possibilities  in  the  principle  and  proceeded  to  try 
out  the  new  type  against  existing  telephones.  On  a  trip 
through  the  East  in  August,  1913,  one  of  the  inventors 
remained  in  Denver,  Colorado,  while  the  other  proceeded 


198 


RADIO   FOR  EVERYBODY 


to  New  York  City. 
Arrangements  were 
then  made  to  get  a 
through  telephone 
connection  from  New 
York  to  Denver.  Such 
arrangements,  h  o  w  - 
ever,  were  not  fav- 
ored by  the  telephone 
companies  as  articu- 
late speech  was  not 
possible  over  that  dis- 
tance of  straight  wire. 
It  must  be  remem- 
bered that  this  was  be- 
fore the  day  of  vac- 
uum tube  repeaters 
and  that  line  condi- 
tions were  very  bad 
over  long  distances. 
After  three  days  the 
connection  was  made, 
and  although  the  in- 
ventors were  warned 
by  the  telephone  com- 
panies that  they  would 
not  be  able  to  under- 
stand each  other,  very 
satisfactory  speech 
was  carried  on  using 
the  electrodynamic 
telephone.  At  the 
same  time,  nothing 
could  be  understood 
over  the  receiver  as 
ordinarily  used.  This 
test  proved  to  the  inventors  that  their  device  had  merit, 
and  that  the  next  problem  was  to  so  condense  and  re- 


A  popular  small  sized  type  of  loud- 
speaker employed  with  the  usual  two- 
stage  amplifier  of  the  radio  receiving: 
set.  A  6-volt  storage  battery  is  used 
to    energize    the    field    coils. 


RADIO   FOR  EVERYBODY 


19^ 


design  their  receivers  so  that  it  would  be  commercially 
practical,  for  complete  it  weighed  60  pounds. 

This  original  receiver  had  a  moving  coil  wound  to  70 
ohms  resistance,  so  that  it  might  be  interchanged  with  the 
ordinary  70-ohm  magnetic  receiver.  This  amount  of  wire, 
however,  was  one  of  the  things  which  made  up  the  weight 
of  the  moving  parts,  and  in  order  that  these  moving  parts 
might  be  made  as  light  as  possible,  the  moving  coil  was 
cut  down  to  20  ohms  resistance  and  a  proper  induction 
coil  supplied  to  fit  it.  The  coils  were  still  wound  fiat  on  a 
mica  sheet,  but  in  or- 
der to  reduce  still  fur- 
ther the  weight  of  the 
complete  instrument, 
one  of  the  electromag- 
nets was  done  away 
with  and  the  little  coil 
was  found  to  function 
perfectly  with  only 
one  side  of  the  coil  in 
the  magnetic  field. 
This  type  was  finally 
developed,  and  was 
the  first  of  the  electro- 
dynamic  receivers  to 
be  commercially  suc- 
cessful, out  of  all  the 
types  which  had  been 
developed  by  the  in- 
ventors thus  far.  This 
tvpe  was  brought  out 
in  July,  1915. 

Immediately  the  re- 
sistance of  the  mov- 
able coil  was  reduced, 
it  was  found  that  the 

receiver    had    loud-       Another    type    of    loxid-speaker,    larger 

4  •  1  ,       .  than  the  one  shown  on  the  facing  page 

Speakmg       cnaractens-       and   intended   for   a   medium-sized   hall. 


200 


RADIO   FOR  EVERYBODY 


tics,  and  still  retained  its  perfection  of  reproduction  of 
speech.  It  was  then  realized  that  no  loud-speaker  could 
be  expected  to  give  forth  loud  speech  unless  sufficient 
modulated  current  was  supplied  to  it,  so  it  became  neces- 
sary for  the  inventors  to  turn  their  attention  for  a  time 
to  the  development  of  a  transmitter  for  use  in  conjunc- 
ion  with  the  electrodynamic  receiver.     A  transmitter  was 


. ... ,     

POLE      PIECES  \^^^ 

i^ 

1 
1 

'wA 

1^ 

'-Bi 

Diaphragm 

MOVABLE 
COIL 

The    mechanism     of    the     electrodynam^ic     type     of     loud-speaker,  • 

consisting:  of  the  pole   pieces  of  the   electro-magnet,  the  movable 

coil,  and  the  diaphragm. 

accordingly  built  that  would  pass  a  little  over  one  ampere 
of  modulated  voice  current  and  deliver  that  amount  to 
the  induction  coil  supplying  the  movable  coil,  attached 
to  the  diaphragm.  It  was  found  that  this  transmitter  in 
conjunction  with  the  electrodynamic  receiver  would  give 
a  volume  of  sound  that  was  enormous  and  which  would 
carry  for  blocks  even  though  the  original  speech  was  no 
louder  than  a  person  would  ordinarily  talk.     This,  then. 


RADIO   FOR   EVERYBODY  201 

was  the  final  stage  in  the  electrical  design  of  the  electro- 
dynamic  receiver,  and  whatever  subsequent  improvements 
were  made  were  along  the  mechanical  rather  than  on  the 
electrical  characteristics  of  the  apparatus. 

Limitations  of  the  Ordinary   Telephone  Receiver 

The  ordinary  telephone  receiver  such  as  is  used  on  our 
present-day  telephone  lines  operates  on  the  electromag- 
netic principle.  The  voice  current  passes  through  a  wind- 
ing on  a  permanent  magnet,  changing  its  flux  intensity 
and  consequently  its  pull  on  a  diaphragm  placed  directly 
over  the  pole  ends.  Its  weakness  lies  in  the  fact  that  if 
the  diaphragm  is  placed  at  a  distance  away  from  the  pole 
pieces  the  magnetic  influence  is  greatly  lessened,  and  if 
placed  too  close  the  diaphragm  hits  the  poles.  A  com- 
promise position  is  selected  whereby  the  diaphragm  is 
placed  at  such-  a  distance  from  the  poles  to  allow  it  some 
motion  before  hitting  the  poles,  and  yet  near  enough  to 
get  a  fair  magnetic  pull.  Another  weakness  is  that  the 
diaphragm  is  under  tension  always  and  has  to  be  made 
stilt  to  withstand  this  tension.  All  types  of  receivers 
using  the  electromagnetic  principle  will  give  forth  sound 
only  up  to  a  certain  point  and  then  the  diaphragm  will  hit 
the  poles. 

In  the  electrodynamic  receiver  the  diaphragm  is  in  no 
way  directly  concerned  with  the  magnetic  flux.  There 
are  no  pole  pieces  to  interfere  with  motion,  which  may  be 
as  great  as  the  elastic  limit  of  the  diaphragm.  A  large 
horn  attached  immediately  above  the  diaphragm  provides 
the  air  column  for  the  diaphragm  to  move.  In  the  present 
instrument  the  field  is  magnetized  to  a  point  approximat- 
ing 20,000  Hues  per  square  centimeter  with  a  current  of 
.6Q  amperes  flowing  in  the  field  coil.  The  movable  coil, 
w4th  a  resistance  of  20  ohms  will  take  car.e  of  approxi- 
mately 10  watts  of  modulated  current  as  supplied  by  an 
amplifier  through  the  proper  step  down  coil  and  will  give 
off  sound  accordingly.  When  it  is  remembered  that  only 
an  extremely  small  fraction  of  a  watt  is  necessary  to  pro- 


202  RADIO   FOR  EVERYBODY 

duce  an  audible  signal,  some  idea  may  be  realized  of  the 
volume  of  sound  generated  by  this  instrument,  produced 
by  the  flow  of  ten  watts.  It  must  be  remembered  also 
that  due  to  the  electrodynamic  principle  involved,  all  of 
the  incoming  energy  is  transferred  into  air  vibrations,  and 
that  the  instrument  is  not  only  capable  O'f  producing  loud 
responses  to  large  inputs,  but  also  is  superior  for  clear 
articulate  response  to  very  small  currents  and  is  fully 
as  sensitive  if  not  slightly  more  so  in  this  respect  than  the 
best  design  of  electromagnetic  receivers. 

Commercial  development  of  this  type  of  receiver  pro- 
ceeded along  several  interesting  and  different  Hues.  For 
receiving  telephone  speech  alone,  without  loud-speaking 
characteristics,  with  a  70-ohm  coil,  a  receiver  was  built 
using  permanent  magnets  to  be  used  on  ships  and  in 
marine  stations  where  communication  was  difficult.  This 
type  of  electrodynamic  telephone,  using  a  double  ear  tube 
arrangement  from  the  diaphragm,  has  become  standard 
equipment  of  United  States  Navy  destroyers  for  marine 
telephone  communication  and  is  being  used  on  hundreds  of 
merchant  vessels  for  the  same  purpose,  in  conjunction 
with  the  anti-noise  transmitter.  The  receiver  can  easily 
he  made  water-tight  and  its  clearness  of  reproduction 
makes  it  indispensable  for  talking  to  the  noisy  engine  room 
of  any  vessel. 

A  phonograph  attachment  was  developed  and  placed  on 
the  market  in  1916  and  consisted  of  an  electrodynamic 
receiver  of  the  loud-speaking  type,  and  its  horn,  a  control 
box  containing  the  proper  induction  coil  and  switches  to 
control  the  current  of  the  device,  and  a  transmitter  tone 
arm.  Many  and  varied  were  the  experiments  necessary 
to  determine  the  proper  location  of  the  transmitter  on 
the  phonograph  tone  arm  in  order  that  needle  scratch  be 
eliminated,  and  yet  perfect  reproduction  of  the  music  be 
maintained.  This  equipment  was  also  supplied  with  a 
hand  transmitter  in  order  that  speech  might  be  amplified 
by  the  same  instrument.  The  voice  and  music  from  a 
phonograph  can  thereby  be  amplified  enormously  for  out- 
door use. 


RADIO   FOR  EVERYBODY  203 

Making  the  Speaker's  Voice  Carry  for  Miles 

Power  vacuum  tube  amplifiers  were  built  and  at  present 
the  apparatus  is  such  that  voice,  words  and  music  have 
been  transmitted  through  the  air  for  over  ten  miles  under 
favorable  conditions  and  a  very  satisfactory  arrangement 
made  whereby  speakers  need  not  hold  the  transmitter  in 
the  hand,  the  amplifier  being  so  sensitive  that  it  will  pick 
up  impulses  through  a  collecting  horn  and  ampHfy  them, 
for  the  assembled  audience.  At  the  same  time  the  electro- 
dynamic  receiver  was  modified  mechanically  and  the  flat 
coil  changed  into  a  circular  one,  still,  however,  moving  in 
a  strong  magnetic  field,  and  unchanged  electrically. 

For  radio  signal  amplification  and  broadcasting,  the 
receiver  is  identical  with  the  exception  that  the  step-down 
coil  is  \yound  to  adapt  itself  to  the  receiving  circuits  of  a 
wireless  receiving  set.  With  ordinary  radio  type  vacuum 
tube  amplifiers  signals  are  received  in  such  volume  as  to 
make  the  use  of  head  phones  unnecessary,  and  also  allow 
•these  signals  to  be  heard  by  large  numbers  of  people.  It 
is  especially  popular  in  the  reception  of  radio  telephone 
speech  and  music. 

The  public  and  commercial  history  of  this  electro- 
dynamic  receiver,  is  very  interesting.  The  inventors  could 
have  done  no  better  when  they  called  the  device  the  "great 
voice,"  deriving  the  name  magnavox  from  the  Latin  words 
magna  and  vox.  It  is  truly  the  great  voice  and  has  had  a 
profound  influence  in  public  affairs  during  the  last  few 
years.  Its  initial  bow  to  the  public  was  made  Christmas 
Eve,  1915,  at  the  Municipal  Christmas  Tree  Celebration 
at  San  Francisco,  California.  That  it  fulfilled  the  expec- 
tations of  the  inventors  may  be  fully  realized  in  the  words 
of  the  San  Francisco  Bulletin  of  the  following  day — 
"The  slender  tone  of  a  single  violin  plainly  heard  a  mile 
away ;  Tetrazzini's  voice  on  a  phonograph  record  resound- 
ing from  end  to  end  of  the  vast  stadium;  the  words  of 
Thos.  W.  Hickey  reading  Lincoln's  Gettysburg  address 
reverberating  like  the  roar  of  a  giant ;  a  piano  solo  resem- 
bling the  chimes  of  Westminster  Abbey,  played  by  a  Co- 


204  RADIO   FOR  EVERYBODY 

lossus  of  Rhodes — these  things  made  possible  by  the  new 
invention." 

After  this  first  demonstration,  attended  by  50,000  peo- 
ple, the  electrodynamic  receiver  has  officiated  at  nearly 
every  large  gathering  of  public  importance  since  the  war, 
where  speakers  needed  amplification  of  the  voices.  During 
the  war  no  demonstrations  were  made  because  of  the  great 
pressure  of  government  orders  in  the  factory.  Several 
notable  examples  are  as  follows :  Ex-President  Wilson 
spoke  at  San  Diego  to  50,000 ;  at  Reno  to  6,000  in  three 
different  theatres  at  the  same  time.  The  Prince  of  Wales 
spoke  to  thirty  thousand  also  at  San  Diego.  The  Victory 
Loan  was  opened  by  an  aviator  delivering  a  speech  by 
radiophone  and  magnavox  to  30,000  at  Washington,  D.  C. 
President  Harding  and  his  political  opponents  used  the 
electrodynamic  loud  speaker  constantly  during  their  cam- 
paign to  talk  to  crowds  varying  from  40,000  to  100,000 
in  the  case  of  ex-Governor  Cox  at  Sheepshead  Bay.  Many 
other  instances  may  be  cited  where  this  apparatus  has 
made  it  possible  for  a  single  speaker  to  address  enormous 
crowds. 

The  electrodynamic  principle  involved  in  the  construc- 
tion of  these  loud-speakers  is  perhaps  the  only  satisfactory 
principle  by  which  a  loud-speaker  may  be  constructed  to 
give  great  volume  from  one  instrument.  There  is  prac- 
tically no  limit  to  the  sound  which  can  be  given  off  by  the 
electrodynamic  receiver,  and  this  volume  of  sound  is 
directly  proportional  to  the  input  of  modulated  voice  cur- 
rent. At  present  the  instrument  will  satisfactorily  take 
care  of  10  watts  of  power  through  the  movable  coil  and 
would  take  care  of  more  if  an  amplifier  were  built  to  give 
more  than  this  amount  in  its  output.  With  10  watts  in 
the  receiver  coil,  however,  an  individual  has  no  trouble  in 
speaking  well  over  a  mile  distinctly  and  can  talk  to  as 
many  people  as  can  conveniently  assemble. 


Chapter  VII. 

TRANSMITTING    THE    DOT    AND 

DASHES    OF    THE    DAMPED 

RADIO  TELEGRAPH 


FOR  those  who  are  satisfied  to  listen  to  what  others 
have  to  say  and  make  absolutely  no  reply,  a  receiving 
set  is  all  that  is  required.  And  the  great  majority  of  radio 
enthusiasts  never  go  beyond  the  receiving  stage,  because 
they  are  satisfied  to  receive  the  radio-phone  concerts  and 
news,  as  well  as  the  dot-dash  messages  of  Government, 
commercial  and  amateur  stations  alike.  When  the  radio 
enthusiast  desires  to  do  a  Httle  "talking""  on  his  own 
account — when  he  tires  of  Hstening  to  others  or  when  he 
wants  to  be  able  to  take  a  hand  in  any  discussion  that 
may  be  taking  place  in  the  ether — he  must  resort  to  a 
transmitter  of  some  sort  or  other  for  generating  the  waves 
that  serve  to  affect  the  apparatus  in  distant  receiving  sta- 
tions. He  may  wish  to  send  in  dots  and  dashes,  or  again, 
he  may  desire  a  radio  telephone  transmitter  in  order  that 
he  may  actually  talk  and  have  his  voice  heard  at  distant 
points ;  but  in  either  event  he  must  go  through  the  for- 
malities of  obtaining  a  station  license  as  well  as  an  oper- 
ator's license,  both  of  which  were  unnecessary  when  he 
confined  his  efforts  to  receiving.  In  this  chapter  we  shall 
deal  only  with  the  simple  radio  telegraph  transmitters, 
leaving  the  more  advanced  types  and  the  continuous  wave 
apparatus,  which  makes  radio  telephony  possible,  for  the 
next  chapter.  Please  note,  however,  tfiat  most  radio  ama- 
teurs are  now  turning  to  the  C.  W.  type  transmitter,  and 
that  spark  or  damped  wave  sets  must -soon  become  obsolete. 


206  RADIO   FOR   EVERYBODY 

What  the  Radio  Transmitter  Does 

Electromagnetic  waves,  by  means  of  which  radio  com- 
munication is  carried  on,  are  produced  by  the  transmitting 
apparatus.  Power  must  be  suppHed  by  some  kind  of 
electric  generator  or  battery ;  this  power  must  be  converted 
into  high  frequency  currents  by  means  of  an  oscillator  or 
wave  generator;  and  the  high  frequency  currents  must 
be  introduced  into  an  aerial  system  consisting  of  the 
aerial  and  the  ground  connection,  in  order  that  the  radio 
waves  may  be  propagated  in  all  directions  through  space. 

Now  the  radio  waves,  as  we  have  already  learned,  may 
be  of   the  damped  or  the  undamped   variety.     Damped 

VVWWWWl 

A  schematic  comparison  between  damped  and  undamped 
waves.  The  damped  waves,  shown  above,  consist  of  w^ave 
groups  or  wave  trains,  while  the  undamped  or  CW  waves 
are  of  uniform  height  and  wave  length  and  without  a  break. 

waves  consist  of  groups  or  trains  of  oscillations  repeated 
at  regular  intervals,  the  amplitude  or  voltage  of  the  oscil- 
lations in  each  train  decreasing  continuously  as  shown  in 
the  accompanying  diagram,  where  the  center  line  indicates 
O  potential,  and  the  length  of  the  line  the  lapse  of  time. 
The  number  of  these  waves  or  trains  per  second  is  some 
audible  frequency.  When  such  waves  strike  a  receiving 
apparatus,  as  we  have  already  learned,  they  cause  a  tone 
in  the  telephone  receiver.  Signals  are  produced  by  means 
of  a  sending  key,  which  lets  the  trains  of  waves  go  on  for 
a  short  time  (producing  a  dot)  or  for  a  longer  time  (pro- 
ducing a  dash).  The  operator  manipulates  the  key  in 
order  to  form  the  dots  and  dashes  which  represent  the 
desired  letters,  numerals,  punctuation  and  other  char- 
acters of  a  dispatch. 


RADIO   FOR  EVERYBODY  207 

The  principles  of  damped  and  undamped  waves  are  the 
same  in  many  respects,  so  that  much  of  what  is  told 
regarding  damped  wave  apparatus  applies  to  undamped 
waves  as  well.  Particular  attention  is  first  given  to 
damped  waves,  as  the  apparatus  is  simple  and  easily  ad- 
justed and  has  long  been  employed. 

Damped  oscillations  or  weaves  are  produced  when  a  con- 
denser discharges  in  a  circuit  containing  inductance.  The 
condenser  is  discharged  by  placing  it  in  series  with  a  spark 
gap  and  applying  a  voltage  that  is  high  enough  to  break 
down  or  spark  across  the  gap.  Such  an  arrangement  is 
presented  in  the  diagram  on  page  208,  where  a  trans- 
former, supplied  with  current  from  a  generator  or  battery, 
charges  the  condenser  placed  across  its  terminals  until  the 
condenser  charge  has  been  built  to  a  point  where  the  spark 
gap  breaks  down.  It  is  as  though  one  were  stretching  a 
rubber  band,  thus  storing  up  considerable  mechanical 
energy,  until  the  breaking  point  was  reached.  Then,  as  the 
rubber  band  snapped,  all  the  stored  up  energy  would  be 
discharged.  When  the  spark  gap  breaks  down  the  pent 
up  energy  of  the  condenser  is  discharged.  Unlike  the 
rubber  band,  how^ever,  the  charge  in  the  condenser  dis- 
charges across  the  gap  and  recharges  the  condenser  in  the 
opposite  direction  to  almost  the  same  extent  as  before, 
followed  by  another  discharge  w^hich  again  charges  the 
condenser  in  the  original  manner  but  of  still  less  extent, 
followed  by  still  another  discharge,  and  so  on  with  the 
current  going  back  and  forth  just  as  does  any  pendulum 
which  has  been  given  a  push,  until  its  swings  or  oscillations 
become  weaker  and  weaker  and  the  pendulum  comes  to 
rest. 

In  discharging,  which  only  requires  the  fraction  of  a 
second,  the  current  passes  through  the  inductance  and  sets 
up  electric  oscillations  which  are  damped  out  or,  to  put  it 
another  way,  soon  reach  zero.  These  discharges,  which 
follow  each  other  in  such  rapid  succession,  form  the  groups 
or  trains  at  regular  intervals. 

Now  the  standard  generator  frequency  for  most  radio 


208 


RADIO   FOR  EVERYBODY 


work  today  is  500  cycles  per  second.  This  causes  the  con- 
denser to  charge  and  discharge  1,000  times  per  second,  or 
once  for  each  positive  and  once  for  each  negative  maxi- 
mum if  the  spark  gap  is  of  such  a  length  as  to  break  down 

Inductance 


Power 
3ou  rc€ 


T^^^Sf^mcr  ^P"'^  <^°P 


The  simplest  kind  of  damped  radio  wave  generator,  consisting 
of  a  power  source,  an  induction  coil  or  transformer  for  stepping 
up  the  current,  a  condenser,  a  spark  gap,  and  an  inductance. 
The  charging  and  discharging  of  the  condenser  through  the  in- 
ductance and  across  the  spark  gap  sets  up  the  oscillations  or 
radio    waves. 


at  the  maximum  voltage  given  by  the  transformer.  The 
number  of  sparks  per  second  is  called  the  spark  frequency. 
With  the  standard  spark  frequency  of  1,000  per  second 
the  amount  of  power  the  set  sends  out  is  considerably 
greater  than  it  would  be  at  the  low  rate  of  60  cycles  per 
second,  because  the  transmitted  radio  waves  are  more 
nearly  continuous.  The  radiated  wave  trains  strike  a 
receiving  antenna  more  frequently  and  their  amplitude 
does  not  need  to  be  as  great  to  produce  the  same  effect  as 
stronger  waves  received  at  longer  intervals  of  time.  The 
higher  frequency  produces  a  tone  in  the  receiving  tele- 
phones that  is  more  easily  heard,  because  the  ear  is  more 
sensitive  to  sound  waves  of  about  1,000  per  second  and 
also  the  tone  is  more  easily  heard  through  atmospheric 
disturbances.  A  60-cycle  supply  may  be  used  if  the  num- 
ber of  sparks  per  second  is  increased  by  the  use  of  a  rotary 
spark  gap  giving  several  sparks  per  cycle,  as  will  be 
described  further  on. 


RADIO  FOR  EVERYBODY 


209 


The  Simplest  of  Transmitters 

Nothing  could  be  simpler  than  the  arrangement  shown 
in  the  accompanying  diagram.  Indeed,  in  the  pioneer 
days  of  radio  such  a  hook-up  was  employed  for  covering 
distances  up  to  100  miles  with  a  10-inch  spark  coil,  and 
back  in  the  crude  beginnings  of  amateur  radio  most  ama- 
teurs made  use  of  a  spark  coil  and  the  plain  aerial  arrange- 
ment here  shown.  In  those  days  the  transmitters  were 
gaged  by  the  inch;  that  is  to  say,  the  amateur  talked  of 
his  transmitter  by  referring  to  the  sparking  distance  of  his 
coil.  Thus  he  had  a  two-inch,  three-inch,  ID-inch  and  so 
on  set,  according  to  his  monetary  resources  or  construc- 
tive ability  as  the  case  might  be. 


The  simplest  form  of  damped  radio  transmitter,  consisting:  of 
a  po-wer  source,  telegrapli  key  for  making:  long:  and  short 
signals  of  the  radio  code,  a  transformer  for  stepping:  up  the 
current,  a  spark  grap,  and  the  aerial  and  the  g:round.  In  this 
arrangement,  known  as  the  plain  aerial  transmitter,  the  aerial 
and    ground    comprise    the    condenser. 

The  arrangement  shown  in  the  diagram  comprises  a 
source  of  power,  a  means  of  raising  the  low  voltage  to  a 
high  one,  say  of  20,000  volts,  which  is  sufficient  to  spark 


210 


RADIO  FOR  EVERYBODY 


across  a  one-inch  gap  between  needle  points,  a  simple  spark 
gap,  a  telegraph  key  for  making  and  breaking  the  primary 
circuit,  and  the  aerial  and  ground  connection.  When  the 
key  is  pressed  the  power  supply  passes  through  the  primary 
of  the  induction  coil  or  transformer,  as  the  case  may  be. 
When  the  current  is  broken,  or  when  the  direction  of  the 
current  is  changed  as  in  the  case  of  alternating  current 
which  is  used  with  a  transformer,  the  secondary  current 
flows  out  into  the  aerial  and  ground,  which  act  as  a  con- 
denser, accumulating  the  charge.  When  the  charge  reaches 
a  certain  point  it  can  no  longer  be  contained  in  the  aerial- 
ground  condenser,  and  consequently  it  dis- 
charges across  the  spark  gap,  setting  up 
oscillations  in  the  aerial  circuit. 

Simple   as   such   a   system   may  be,   it   is 
hardly     permissible     in 

general  practice  for  the  Tunlna         le 

good    reason    that    the         Inductance  S 
waves    emitted    are    of  )^ 

such   broad   wave  length   that   they  j^ 

cannot  be  readily  tuned  out  at  the  g 

receiving    end.      Any    amateur    of 
long  experience  can  tell  you  stories 


How  inductance  is  added  to  vary  the 
wave  lengrth  of  the  aerial.  In  this  in- 
stance the  same  apparatus  as  shown 
on  page  209  is  employed,  but  a  tuning 
inductance,  known  as  an  aerial  induc- 
tance or  loading   coil,   is  added. 


of  the  days  before  the  present  radio  laws,  when  it  was 
possible  with  even  a  one-inch  coil  and  other  simple  ap- 


RADIO   FOR  EVERYBODY  211 

paratus  to  prevent  the  most  powerful  stations  from  carry- 
ing on  their  business,  if  the  amateur  transmitter  happened 
to  be  located  a  short  distance  away.  The  one-inch  coil 
simply  monopolized  the  ether  in  its  immediate  vicinity. 
It  came  in  loudly  at  almost  any  point  on  the  tuner,  so 
that  it  could  not  be  tuned  out  in  order  to  receive  a  signal 
from  a  distant  transmitter.  However,  it  does  not  carry 
for  any  distance,  so  that  outside  of  deliberate  interference 
it  was  of  no  real  value.  Furthermore,  one  of  the  first 
things  which  the  radio  law  accomplished  was  to  put  an 
end  to  these  broadly  tuned  transmitters  and  in  their  place 
insisted  on  transmitters  whose  emitted  waves  must  be 
sufficiently  sharp  so  as  to  have  them  interfere  as  little  as 
possible  with  other  waves. 

The  plain  aerial  arrangement,  as  this  layout  is  called,  has 
other  advantages  aside  from  its  simplicity.  Its  effective- 
ness comes  in  when  the  sending  operator  wants  all  possible 
stations  to  hear  him  immediately,  as  for  instance  when  a 
ship  is  sending  out  a  distress  call.  At  such  a  time  inter- 
ference is  a  desirable  thing,  because  the  distress  call  must 
be  heard  by  every  possible  receiving  station  within  range. 
With  the  regular  sharply  tuned  waves,  a  receiving  oper- 
ator may  never  hear  the  signals  for  the  reason  that  his 
receiver  is  adjusted  for  another  wave  length  and  is  too 
sharply  tuned  to  respond  to  a  sharply  tuned  wave.  The 
broadly  tuned  wave,  on  the  other  hand,  can  be  heard  with 
almost  any  receiving  set  adjustment.  The  plain  aerial  has 
also  a  definite  advantage  in  military  activities  for  the 
purpose  of  drowning  out  or  "jamming"  the  enemy's  sig- 
nals. For  amateur  purposes,  however,  the  plain  aerial 
arrangement  is  a  thing  of  the  past. 

A  modification  of  the  plain  aerial  arrangement  is  shown 
on  the  preceding  page,  which  has  a  tuning  inductance  in 
the  aerial  circuit  so  that  wave  length  of  the  emitted  waves 
may  be  varied  to  some  extent.  Placing  a  condenser  in  the 
aerial  or  ground  lead  also  varies  the  wave  length,  but 
instead  of  increasing  it,  as  is  the  case  with  inductance, 
it  decreases  the  wave  length. 


212 


RADIO   FOR  EVERYBODY 


The  Transmitting  Aerial 

In  transmitting  the  aerial  problem  is  far  more  involved 
than  it  is  for  receiving.  As  we  have  already  learned,  a 
single  wire  of  almost  any  length  or  even  a  bed-spring 


Inverted  Ir-type  aerial,  with  the  lead-in  taken  oflf  at  one  end. 

or  fire-escape  or  other  mass  of  metal  will  do  for  an  an- 
tenna in  connection  with  a  good  receiving  set,  but  the 
aerial  of  a  transmitting  set  must  be  properly  constructed 
if  satisfactory  results  are  to  be  obtained. 

To  begin  with,  a  single-wire  aerial  is  unsatisfactory 
for  transmission  purposes.  Two  or  more  wires  must  be 
used,  and  four  wires  or  more  give  the  best  results.    Then 


T-type  aerial,  with  the  lead-in  taken  oflF  the  middle  of  the 
aerial     span. 

the  height  is  important;  the  aerial  should  never  be  less 
than  25  feet  above  the  ground  or  roof,  and  preferably  50 
feet  or  more. 

In  the  accompanying  diagrams  several  types  of  trans- 
mitting aerials  are  shown.  The  most  common  is  the  in- 
verted L-type,  with  the  lead-in  at  one  end.  The  T-type 
should  be  used  when  the  span  is  greater  than  100   feet 


RADIO   FOR  EVERYBODY 


213 


in  order  to  reduce  the  natural  wave  length  of  the  aerial. 
The  umbrella  aerial  should  be  used  when  one  is  working 
in  a  crowded  space  and  there  is  no  room  for  the  usual 
types  of  aerials.  The  umbrella  aerial  makes  use  of  a 
single  tall  mast,  with  wires  radiating  downwards  in  all 
directions.  The  lower  ends  of  the  wires  should  be  at  least 
20  feet  away  from  the  base  of  the  mast. 

The  construction  of  the  transmitting  aerial  is  consider- 
ably more  involved  than  that  of  the  receiving  antenna. 
It  must  be  larger  and  therefore  stronger,  and  it  must  be 
better  insulated  because  it  is  handling  high-voltage  cur- 
rents.    The  drawing  on  page  215   gives  a   few  pointers 


The   V-type  aerial — a  rare  type  which    should  only  be   em- 
ployed when  a  suflScient  span  cannot  be  obtained,  thus  mak- 
ing a   double   aerial  of  this  kind  desirable. 

concerning  the  construction  of  a  good,  substantial  multi- 
wire  aerial  for  transmitting  purposes.  Note  that  the  ends 
of  each  wire  are  insulated  with  hard  rubber  rods  pro- 
vided with  screw-eyes  at  each  end,  or  with  regular  elec- 
trose  insulators.  As  a  further  precaution,  insulators  may 
be  inserted  in  the  ropes  or  wires  supporting  the  spreaders, 
as   the   sticks   supporting  the  wires   are  called.     Pulleys 


214  RADIO   FOR  EVERYBODY 

are  provided  on  the  supports  of  the  aerial,  so  that  the  lat- 
ter may  be  raised  or  lowered  at  will  for  inspection  and 
repairs.  Guy  ropes  or  wires  are  arranged  with  insulators 
for  the  purpose  of  keeping  the  aerial  perfectly  flat,  despite 
wind  and  the  unequal  sag  of  the  wires.  The  lead-in  wires 
are  taken  off  each  wire  of  the  aerial,  brought  down  a  con- 
siderable distance  to  a  point  where  they  converge  into 
one  lead-in  cable,  just  before  entering  the  station.  The 
special  electrose  lead-in  insulator  shown  makes  a  very  neat 
lead-in  arrangement.  It  will  be  noted  that  this  insulator  is 
provided  with  a  brass  rod  passing  through  it,  both  ends 
of  the  rod  being  equipped  with  nuts  and  lugs  for  making 
connections. 

The  strop  or  egg  insulator  is  a  popular  form  of  insula- 
tor for  the  reason  that  it  possesses  great  strength  and 
good  insulating  properties.  Furthermore,  in  the  event  of 
mechanical  failure,  it  will  be  noted  that  the  two  wires  or 
ropes  passing  through  different  holes  in  this  insulator 
merely  come  together,  so  that  the  mechanical  arrange- 
ment still  holds  fast  even  if  the  insulation  arrangement 
may  be  broken  down. 

The  same  aerial  may  be  used  for  receiving  and  trans- 
mitting. In  former  days  the  same  aerial  was  always  used 
for  both  purposes.  The  aerial,  in  such  a  case,  is  designed 
with  the  transmitting  end  in  view,  since  any  good  trans- 
mitting aerial  gives  good  results  with  a  receiving  set.  In 
order  that  the  same  aerial  may  be  used  for  both  purposes, 
a  send-receive  or  aerial  change-over  switch  is  employed. 
This  switch  is  connected  with  the  aerial  and  with  the  re- 
ceiving and  the  transmitting  sets  in  such  a  manner  that 
when  it  is  thrown  one  way,  the  aerial  is  connected  with 
the  receiving  set,  and  is  used  for  receiving,  and  when  it 
is  thrown  the  other  way,  it  is  connected  with  the  transmit- 
ting set  and  is  ready  for  transmitting.  Obviously,  it  would 
not  do  to  have  the  receiving  set  connected  with  the  aerial 
at  the  same  time  as  the  transmitter,  since  the  latter,  with 
its  powerful  output,  would  cause  damage  to  the  delicate 
receiving  apparatus. 


RADIO   FOR   EVERYBODY 


!15 


Many  amateurs  today  prefer  to  use  a  separate  aerial 
and  antenna  for  transmitting  and  receiving.  The  aerial 
and  antenna  are  connected  with  a  single  switching  device 
in  such  a  manner  that  only  one  of  them  can  be  used  at  a 


Maif 


MA*t 


•Ssz 


6Tro^  OP  «^  insylAtor 


L!ectrod«.    InsoUTo**  for 
CArryifN^  LeAd-i'r\  Wire5 


Constructional    details    of   a   good    flat-top    transnaitting    aerial, 
the   strop   or  egg  type  insulator,   and   the   electrose  lead-in  in- 
sulator. 

time,  so  as  to  preclude  operating  the  transmitter  while 
the  receiving  set  is  connected  with  its  antenna  but  a  short 
distance  away. 

In  transmitting  work  a  good  ground  is  necessary,  for 
the  best  results.  A  ground  that  is  imperfect  or  of  high 
resistance  will  take  away  from  the  transmitting  range  in 
no  little  degree. 


216 


RADIO   FOR  EVERYBODY 


Transmitters  That  Are  Sharply  Tuned 

Single-circuit  transmitters  are  not  permitted  under  the 
present   radio   laws,    for  the   reason  that  ^        . 
the    waves    emitted    are    not    sufficiently  I    '    '  ^ 
sharp.    Too  much  cannot  be  said  in  favor 
of  the  radio  laws  -in  this  direction;  any 


IT 


5G 


Tunincj^ 

Inductance 
o  or  Helix 


Simple  transmitter  arrangement  for  producing  fairly  sharp 
waves  of  the  damped  variety.  PS — power  source;  K — telegraph 
key;  T — transformer;  C — condenser;  SG — spark  gap;  A  and 
G — aerial   and    ground;    and    the   tuning    inductance    or   helix. 

one  who  has  been  listening  in  to  the  radio-phone  service 
must  have  experienced  the  annoyance  of  some  spark  sta- 
tion breaking  in  on  the  mus'ic.  It  is  only  by  assigning 
certain  wave  length  bands  to  the  various  classes  of  trans- 
mitters, and  insisting  that  their  waves  be  kept  sharply 
tuned  within  narrow  tolerances,  that  interference  can  be 
reduced  to  a  minimum. 

In  order  to  emit  sharp  waves  which  come  within  the 
stipulations  of  the  radio  laws,  it  is  necessary  to  produce 
the  oscillations  in  a  closed  circuit  which  is  directly  or 
inductively  coupled  to  the  aerial  or  ''open"  circuit.  Such 
an  arrangement  is  shown  in  the  diagram  on  page  217, 
where  the  induction  coil  or  transformer  serves  to  charge 
the  condenser,  which  discharges  across  the  spark  gap  and 
through  the  inductance.  The  inductance^  it  will  be  noted, 
forms  part  of  the  "closed"  or  oscillating  circuit  and  also 
part  of  the  aerial  or  "open'"  circuit.  Thus  it  serves  as 
an  auto-transformer,  as  a  single  coil  transformer  is  called. 
Any  number  of  turns  of  this  inductance    which  is  made 


RADIO   FOR  EVERYBODY 


217 


up  of  a  number  of  turns  of  heavy  wire  or  strip,  may  be 
cut  into  the  closed  circuit  and  into  the  open  circuit,  so  as 
to  estabhsh  the  proper  ratio  between  the  circuits.  The 
positions  of  the  spark  gap  and  the  condenser  are  sometimes 
interchanged,  bringing  the  spark  gap  across  the  trans- 
former. There  is  practically  no  difference  in  the  oper- 
ation, as  a  result  of  such  a  change. 

In  connecting  up  the  various  components  of  a  trans- 
mitting set,  heavy  wire,  certainly  not  less  than  No.  12, 
insulated  or  bare,  should  be  used.  It  is  preferable  to 
use  copper  strip,  if  possible,  since  it  has  a  greater  surface 
area  and  the  currents  with  w.hich  we  are  now  dealing 
travel  on  the  suface  rather  than  through  the  entire  con- 
ductor. The  conductors  should  be  neatly  run  from  one 
connection  to  the  next,  and  arranged  so  as  not  to  come 
near  one  another  because  of  the  danger  of  sparking.  Fur- 
thermore, the  conductors  must  be  kept  as  short 
as  possible,  for  in  a  transmitting  set  the  induc- 
tance represented  by  a  few  feet  of  conductor 
is  sufficient  to  make  the  wave  *  ....  • 
length  of  the  oscillating  cir-     Addjf.onal 

.^  ,  .      t.  11       InciucTancc  tor 

cuit   SO  great  as   to  be   well     ^  Y/aves 

beyond  the  permissible  200-  -* 

meter  wave  lensth   of   ama- 


SG 

Short  wove 
Condenser 


Same  arrangement  as  shown  on  the  fac- 
ing page,  but  with  an  aerial  inductanoe 
or  loading  coil  for  increasing  the  w^ave 
length,  and  a  ground  series  condenser  for 
reducing  the  wave  length,  of  the  aerial- 
ground    circuit. 


218 


RADIO   FOR  EVERYBODY 


teur  transmission.  So  the  components  must  be  placed 
close  together,  and  connected  with  the  shortest  possible 
conductors.  This  also  applies  to  the  connection  with  the 
aerial,  which  should  be  made  as  short  and  as  direct  as 
possible,  in  order  to  secure  high  efficiency  and  keep  within 
the  wave  length  requirements. 

In  order  to  determine  the  proper  number  of  turns  for 
the  closed  and  the  open  circuits,  the  usual  method  for  the 
amateur  is  to  use  a  measuring  device  known  as  a  hot-wire 
ammeter  in  the  aerial  circuit,  for  the  purpose  of  measuring 
the  aerial  current.  Approximate  results  may  be  obtained 
by  the  use  of  a  low  resistance  lamp,  such  as  a  small  auto- 
mobile lamp  or  even  a  pocket  flashlamp  -bulb.  The  lamp 
is  used  in  place  of  the  hot-wire  ammeter,  the  maximum 
current  in  the  aerial  being  indicated  by  the  maxi- 
mum brightness  of  the  lamp  filament.  If  the 
current  is  apt  to  be  too  great   for  the  lamp,   it 


Transm  ittinoj 
Coupler 

Simple       spark      transmitter      for      producing:  I     Q 

sharply    tuned    waves    of    the    damped    variety.  | 

In   this   case  a  transmitting    coupler   or   loose-  • 

coupler  arrangement  is   employed,   so   that  the  -rz- 

oscillating   or  closed   circuit   is   entirely    separ- 
ated   from   the    open    or    aerial-ground    circuit. 
The  primary  P  and  the  secondary   S  comprise 
the    transmitting    coupler. 

should  be  shunted  by  a  few  turns  of  wire.  The  ammeter 
and  lamp  must  be  eliminated  or  even  short-circuited  ex- 
cept when  actually  needed,  in  order  to  keep  the  resistance 
of  the  aerial  circuit  down  as  low  as  possible. 

In  actual  practice,  the  closed  circuit  is  first  adjusted  to 
the  desired  wave  length,  which  can  best  be  determined  by 


RADIO   FOR  EVERYBODY  219 

the  use  of  an  instrument  known  as  a  wave  meter.  Then 
the  aerial  circuit  is  adjusted  until  the  lamp  or  hot-wire 
ammeter  indicates  the  maximum  output,  proving  that  the 
two  circuits  are  in  resonance.  Most  of  the  progressive 
radio  clubs — and  there  are  radio  clubs  in  practically  every 
part  of  the  country — ^^have  wave  meters  for  the  use  of  their 
members.  The  best  method  of  tuning,  aside  from  waiting 
for  the  radio  inspector  to  tune  the  transmitter  when  he 
comes  to  inspect  it,  is  to  call  upon  the  local  radio  club  for 
aid  in  this  direction. 

One  method  largely  employed  by  amateurs  in  tuning 
their  transmitters  is  to  adjust  their  oscillating  circuit  and 
then  the  aerial  circuit  for  maximum  output,  after  which 
they  ask  a  radio  friend  to  listen  in  on  his  receiving  set  to 
the  test  signals  and  to  determine  whether  they  are  higher 
or  lower  in  wave  length  than  those  of  other  amateur  sta- 
tions known  to  be  tuned  to  a  wave  length  below  200 
meters,  which  is  the  maximum  set  for  amateur  transmis- 
sion.    This  latter  method,  however,  is  not  very  accurate. 

In  most  instances  it  is  best  to  wait  until  the  radio  inspec- 
tor comes  to  the  station  in  order  to  check  up  the  trans- 
mitted wave  lensrth.  The  inspector,  being  provided  with 
a  wave  meter,  sees  to  it  that  the  station  is  emitting  a  wave 
within  the  set  limits  and  also  that  the  wave  is  sufficiently 
pure  or  sharp  to  comply  with  the  law. 

At  this  point  it  is  well  parenthetically  to  point  out  that 
the  transmitter  problem  may  be  materially  simplified  by 
purchasing  a  complete  transmitter  in  one  unit.  Today  the 
practice  is  to  make  the  transmitter  apparatus  into  one 
simple  unit  in  the  form  of  a  panel,  the  controls  and 
meters  being  placed  on  the  front  face,  and  the  various 
components  at  the  rear.  Such  a  transmitter  has  wave 
length  adjustments  and  hot-wire  ammeter,  as  well  as  other 
controls  which  simplify  the  tuning  and  general  operation. 

If  a  complete  transmitter  is  not  employed,  then  it  is 
necessary  to  purchase  separate  pieces  of  apparatus  and  to 
arrange  them  in  some  suitable  manner.  Any  radio  supply 
house  will  gladly  furnish  the  necessary  technical  assistance 


220  RADIO   FOR  EVERYBODY 

in  the  installation  of  a  radio  transmitter.  Then  again,  if 
one  has  cultivated  the  friendship  of  the  radio  amateurs 
in  the  general  vicinity,  one  can  obtain  all  the  necessary 
help  in  this  direction. 

So  much  for  the  directly-coupled  set  which  we  have  so 
far  discussed,  and  the  tuning  of  a  transmitter.  There  is 
another  arrangement  known  as  the  loose-coupled  set,  which 
is  shown  in  the  diagram  on  page  219.  Here  the  closed 
and  the  open  circuits  are  not  connected  directly,  but  are 
inductively  coupled.  Such  an  arrangement  makes  for 
sharper  waves  and  a  high  degree  of  efficiency.  The 
coupling  may  be  varied  so  as  to  obtain  the  best  results,  the 
adjustment  depending  largely  on  the  type  of  gap  employed. 

The  Question  of  Transmitting  Condensers 

The  most  common  types  of  condensers  used  in  radio 
transmitting  circuits  employ  mica  or  glass  as  the  dielectric, 
with  tinfoil  or  thin  copper  as  the  conducting  coatings. 
Compressed  air  and  oil  condensers  are  sometimes  used  in 
professional  work,  but  they  are  balky  and  certainly  well 
outside  of  the  province  of  the  amateur.  For  very  high 
voltages  the  condenser  plates  are  sometimes  immersed  in 
oil  to  prevent  brush  discharge.  Brush  discharge  is  the 
leakage  of  current  which  takes  the  form  of  tiny  purple 
streamers  or  sparks  about  the  edge  or  any  conductor  of 
high  voltage  current.  For  moderate  voltage  a  coating  of 
paraffin  over  glass  plates,  especially  at  the  edges  of  the 
metal  foil,  will  satisfactorily  reduce  brush  discharge. 
Today,  however,  the  amateur  is  indeed  fortunate  in  that 
his  condenser  problem  is  solved  by  purchasing  one  or  the 
other  of  the  several  manufactured  condensers  which  come 
in  compact  molded  units,  or  in  wooden  or  metal  cases. 
A  condenser  of  suitable  size  can  be  obtained  in  one  unit 
or  built  up  of  several  units. 

The  transmitting  condensers  mostly  used  today  are  of 
the  mica  insulated  type.  These  condensers  have  been 
found  to  be  superior  to  any  other  type.  Each  mica  con- 
denser is  composed  of  several  sections  or  units  enclosed 


INOiCATING 
'IMSTRUMCNTa 


*! 


MOTOR- GENERATOR 
'•COrsTROLS 


I      COUPUNQ, 
^<"CONTROl_ 


we:  length 

CNTROL.S 


auENCHED    GAP 


>WER   CONTROL 
"iNEL. 


Panel  type  damped  wave  transmitter,  such  as  is  employed  on 
board  steamers.  This  transmitter  makes  use  of  a  quenched  grap, 
which   is    mounted    on    the   front    of   the    panel.     (See    page    223. > 


^^22  RADIO  FOR  EVERYBODY 

in  a  common  casing  of  aluminum  or  wood,  depending  upon 
the  capacity  and  voltage.  Each  of  these  sections  or  units 
comprises  alternating  sheets  of  mica  and  foil,  over  a 
thousand  in  number.  The  sections  or  units  thus  con- 
stituted are  piled  on  top  of  one  another  in  the  aluminum 
casing,  and  each  section  or  unit  is  separated  from  the 
next  by  a  sheet  of  mica.  The  sheets  of  mica  are  larger 
than  the  sheets  of  foil,  so  as  to  avoid  any  brush  discharge 
at  the  edges. 

Air,  moisture,  and  small  vacuum  pockets  must  be  elimi- 
nated from  each  section  or  unit,  hence  an  insulating  ad- 
hesive of  special  composition,  having  the  required  dielec- 
tric properties,  is  forced  through  the  entire  condenser. 
The  moisture  and  air  are  expelled,  and  the  vacuum  pockets 
are  filled  with  this  adhesive,  which  is  deposited  in  a  thin 
layer  on  each  of  the  thousand  sheets  of  mica.  Next  a 
melted  wax  compound  is  poured  into  the  aluminum  casing, 
so  as  to  fill  any  empty  spaces  between  the  condenser  sec- 
tions or  units  and  the  case. 

Before  the  wax  has  hardened  a  pressure  plate  is  placed 
on  the  topmost  section  or  unit.  After  the  cover  is  screwed 
on,  this  plate  presses  all  the  sections  together.  Because 
they  are  pressed  together,  the  sections  cannot  move  about. 
It  is  highly  important  that  the  spacing  between  the  metal 
foil  and  the  mica  be  kept  constant — an  end  secured  by  the 
use  of  the  pressure  plate.  A  post  passes  up  through  the 
cover  of  the  case  and  serves  as  one  terminal,  the  case 
serving  as  the  other  when  metal  is  used  for  the  case. 

The  efficient  use  of  the  space  inside  the  condenser — 
the  active  surfaces  taking  up  the  larger  part  of  this  volume 
— is,  of  course,  a  big  factor  in  making  the  mica  condenser 
a  fractional  part  of  the  size  of  the  glass  plate  or  Leyden 
jar  condensers  of  equal  capacity.  The  Leyden  jar  con- 
densers are  the  bottle-like  contraptions  with  an  inside  and 
outside  tinfoil  coating,  seen  in  physics  laboratories  and  in 
connection  with  X-ray  and  electro-therapeutic  apparatus. 
Yet  the  mica  condenser  has  2,000  square  inches  of  active 
surface  as  compared  with  175  square  inches  for  a  glass 
dielectric  condenser  of  equivalent  capacity  and  voltage. 


RADIO   FOR   EVERYBODY 


223 


Since  the  mica  condenser  consists  of  over  a  thousand 
sheets  of  mica  and  foil,  the  full  voltage  across  the  trans- 
former is  minutely  subdivided.  Hence  the  potential  that 
does  act  across  a  single  unit  is  so  very  small  that  there  is 


lK 

si 

y 

AERi'^^i.    iNDUCTANCE 

infa 

fS3i 

:|i»; ..  SiSill 

wi 

^i 

^H 

li 

^B 

WAV  E  -  u  £  N ;.  r  k  Sa|^9P# 

CHAN61N0    1  H^K^^F  M 

SVytTCHELS      1   gB|HB  1 

K1  icA -""^^n^^BiliH 

;  CONDENSERS      ^m^^^^^^^M 

,^^^4^            1                   ,:;V|f" 

1 

■TRANSFORMER- 
^CASING 

Panel   type   damped   wave   transmitter,   the   front   view   of   which 

appears    on    page    221.      Simple    as   the    front    view    may    seem,    it 

will  be  noted  that  the  transmitter  is  quite  complicated  with  most 

of  its  mechanism  mounted  at  the  rear  of  the  panel. 


224  RADIO   FOR  EVERYBODY 

no  destructive  brush.  The  losses  m  the  dielectric  increases 
greatly  with  the  voltage.  Therefore,  if  the  voltage  of 
each  section  in  the  condenser  is  reduced  markedly,  the 
problem  of  preventing  the  brush  discharge  is  met.  It  is 
better  to  control  several  hundred  volts  in  this  manner  than 
twenty-thousand  volts  individually. 

When  the  spark  gap  of  a  transmitter  is  broken  down  by 
the  high  voltage  it  becomes  a  conductor,  and  readily  allows 
the  oscillations  of  the  condenser  discharge  to  pass.  Dur- 
ing the  interval  between  discharges  the  gap  cools  off  and 
quickly  becomes  non-conducting  again.  If  the  gap  did 
not  resume  its  non-conducting  condition,  the  condenser 
would  not  be  charged  again,  since  it  would  be  short- 
circuited  by  the  gap,  and  further  oscillations  could  not  be 
produced.  The  restoration  of  the  non-conducting  state  is 
called  ''quenching."  A  device  called  the  quench  gap  is 
described  further  on. 

Spark  Gaps  of  All  Kinds 

A  plain  spark  gap  usually  consists  of  two  metal  rods  so 
arranged  that  their  distance  apart  is  closely  adjustable. 
The  gap  must  be  kept  cool,  so  that  the  discharge  will  not 
arc  and  to  this  end  the  rods  are  often  provided  with  cooling 
fins.  The  length  of  the  gap  which  can  be  employed  is 
limited  by  the  voltage  that  the  transformer  is  capable  of 
producing,  the  ability  of  the  condenser  dielectric  to  with- 
stand the  voltage,  and  the  -fact  that  for  readable  signals 
the  spark  discharge  must  be  regular.  If  the  gap  is  too 
long,  sparks  will  not  pass,  or  only  at  irregular  intervals. 
If  the  gap  is  too  short,  it  may  arc  and  burn  the  electrodes. 
Even  if  no  arc  takes  place,  the  voltage  is  reduced  by  too 
short  a  gap  and  this  results  in  reduced  power  and  range. 
The  length  for  smooth  operation  can  usually  be  determined 
by  trial. 

It  is  found  that  a  short  gap  between  cool  electrodes  is 
quenched  very  quickly,  the  air  becoming  non-conducting 
almost  immediately  after  it  has  broken  down,  or  as  soon 
as  the  current  falls  to  a  low  value.  This  action  is  also 
improved  if  the  spark  gap  is  enclosed  in  an  air-tight  cham- 


POWER  SUPPLY 
AND   AERIAL 
AMMETERS 


AERIAL   INDUCT- 
ANCE   CONTROL 


WAVE   LENGTH 
CONTROL. 


SPEED   AND    VOLT 
AGe     CONTROL 


COUPLING 
CONTROL 


QUENCHED 
SPARK-GAP 


ENCLOSED 
3VNCHROMOt*-S 
RO-r/VRY    GAP- 
OrM    GENERATOR 
SHAFT 


MOTOR 

GENERATOR 

CONXRO 

PANEL 


Another  type  of  damped  wave  transmitter,  such  as  is  nsed  on 
board  ship.  In  this  instance  there  are  two  methods  of  obtaining: 
the  oscillations  or  waves.  There  is  the  quenched  pap  mounted 
on  the  front  of  the  panel,  and  the  synchronous  rotary  gap 
mounted    at    the    right. 


226  RADIO   FOR   EVERYBODY 

ber.  The  standard  form  of  quenched  gap,  as  such  a  gap 
is  called,  consists  of  a  number  of  flat  copper  or  silver 
disks  of  large  area,  say  three  or  four  inches  in  diam- 
eter at  the  sparking  surfaces,  with  their  faces  separated  by 
a  space  about  the  thickness  of  a  piece  of  heavy  paper.  To 
provide  the  necessary  total  length  of  gap  for  high  voltage 
charging,  a  number  of  these  small  gaps  are  put  in  series, 
so  that"  the  spark  must  jump  them  all,  one  after  the  other. 
The  disks  are  separated  by  rings  of  mica  or  paper.  The 
larger  gaps  handling  considerable  power  are  kept  cool  by 
means  of  a  small  fan  or  blower.  But  all  quenched  gaps 
are  provided  with  projecting  fins  for  radiating  heat,  and 
in  some  designs  air  spaces  are  provided  between  the  pairs 
of  disks  which  form  the  successive  gaps.  The  number  of 
gaps  is  determined  by  the  voltage,  allowing  about  1,200 
volts  per  gap.  Eight  or  ten  gaps  are  sufficient  in  most 
transmitters  of  this  type. 

The  quenched  gap  is  not  used  in  sets  having  a  supply 
frequency  as  low  as  60  cycles  per  second.  The  sparks 
obtained  at  that  frequency  are  found  to  be  irregular  and 
not  of  a  good  tone.  For  this  case,  a  rotary  gap  is  used, 
as  will  be  explained.  For  500-cycle  supply  the  quenched 
gap  is  adjusted  to  break  down  at  the  maximum  value  of 
the  applied  voltage;  that  is,  with  its  total  length  so  ad- 
justed as  to  give  one  spark  for  each  half  cycle  of  the 
applied  current.  Discharges  at  other  times  are  not  pos- 
sible, and  as  a  result  of  this  regularity  a  clear  note  is 
obtained.  One  advantage  of  the  quenched  gap  is  that  it 
aids  the  production  of  a  so-called  pure  wave — one  which 
is  sharply  tuned.  It  has  also  the  advantage  of  being  noise- 
less in  operation,  on  account  of  the  very  short  gaps  and  the 
enclosure  of  the  spark. 

A  500-cycle  current  supply  may  be  obtained  by  using 
what  is  known  as  a  motor-generator — a  motor  operating 
oflf  the  usual  supply  current,  directly  connected  with  a 
500-cycle  alternating  current  generator  which  supplies 
current  for  the  radio  transmitter.  Such  motor-generator 
sets  may  be  obtained  in  a  wide  range  of  capacities  for 
the  smallest  as  well  as  the  largest  transmitters. 


RADIO   FOR   EVERYBODY  227 

A  rotary  gap  consists  of  a  wheel  with  projecting  points 
or  knobs,  with  a  stationary  electrode  on  each  side  of  the 
wheel.  The  spark  jumps  from  one  stationary  electrode 
to  one  of  the  moving  points,  flows  across  the  wheel,  and 
then,  after  leaping  the  corresponding  gap  on  the  other 
side,  passes  out  at  the  second  stationary  electrode.  The 
number  of  sparks  per  second  is  thus  determined  by  the 
speed  of  the  wheel  which  is  motor-driven,  so  that  signals 
of  high  pitch  can  be  produced.  An  advantage  of  the 
rotary  gap  is  the  prevention  of  arcing,  because  of  the 
motion  of  the  wheel  and  the  fanning  effect,  and  because 
the  electrodes  brought  successively  up  to  the  spark  gap 
have  time  to  cool  in  their  idle  intervals. 

There  is  still  a  more  elaborate  form  of  spark  gap  which 
is  seldom  found  in  amateur  work  but  which  mi'ght  as  well 
be  mentioned  here,  since  we  have  covered  practically  all 
forms  of  transmitters  of  the  damped  wave  category.  This 
more  elaborate  form  is  known  as  the  synchronous  rotary 
gap.  The  wheel  of  the  rotary  gap  is  mounted  on  the  shaft 
of  the  motor-generator  set  which  furnishes  the  alternating 
current.  The  mounting  is  such  that  the  spark  points  or 
electrodes  are  brought  opposite  each  other  at  just  the  mo- 
ment w^hen  the  alternating  current  voltage  in  the  condenser 
reaches  its  maximum  value,  positive  and  negative.  Thus 
500  cycles  will  produce  1,000  sparks  per  second.  This 
regular  occurrence  of  the  discharges  gives  smooth  and 
efficient  operation,  as  well  as  a  pure  musical  tone.  A 
rotary  gap  that  is  not  so  timed  with  the  alternating  cur- 
rent supply  is  called  non-synchronous. 

Attempts  to  produce  a  high  pitch  spark  with  a  60-cycle 
source  by  means  of  a  synchronous  gap  giving,  say,  exactly 
six  sparks  per  half  cycle  have  not  given  satisfaction,  be- 
cause the  applied  voltage  is  not  the  same  at  the  time  of 
the  different  sparks,  and  while  the  note  is  of  high  pitch, 
it  is  not  musical.  It  has  been  found  better  to  use  a  non- 
synchronous  gap  in  such  case,  producing  a  large  number 
of  sparks  per  second  and  letting  them  occur  wherever 
they  may  happen  during  the  cycle.    The  irregularities  will 


228  RADIO   FOR  EVERYBODY 

somewhat  balance  up.  While  the  tone  is  not  strictly  musi- 
cal, it  can  be  made  of  high  pitch.  The  non-synchronous 
gap  is  best  used  if  nothing  but  a  60-cycle  or  other  low 
frequency  source  is  available.  Such  a  low  frequency, 
however,  is  being  avoided  in  modern  apparatus,  the  stan- 
dard frequency  being  500  cycles  per  second.  But  for  the 
amateur  who  cannot  go  to  the  expense  and  trouble  of  a 
small  motor-generator  set  for  generating  a  500-cycle  cur- 
rent, the  rotary  gap  will  be  found  quite  satisfactory  on 
60-cycle  supply. 


Chapter  VIII. 

THE  RADIO  TELEPHONE  TRANSMIT- 
TER AND  THE  CW  TELEGRAPH 
TRANSMITTER 


THE  transmitters  described  in  the  previous  chapter  are 
of  the  damped  or  discontinuous  variety.  They  are 
suitable  for  radio  telegraph  purposes,  although  the  con- 
tinuous or  undamped  wave  type  has  proved  to  be  so  much 
better  than  the  former  that  more  and  more  radio  amateurs 
have  turned  to  this  latter  method.  The  continuous  wave 
transmitter  carries  farther  with  a  given  amount  of  power ; 
the  equipment  is  in  many  respects  simpler;  it  is  silent  in 
operation;  it  can  be  interchangeably  used  for  radio  tele- 
graph or  radio  telephone. 

We  have  already  learned  that  damped  weaves  are  sent 
out  in  trains  or  groups,  and  that  the  oscillations  in  each 
train  or  group  die  down  or  are  damped  rapidly.  The  un- 
damped or  continuous  waves,  known  as  CW  for  short, 
are  not  damped,  nor  do  they  die  down.  The  waves  are 
continuous  just  so  long  as  the  transmitter  is  operated. 
The  only  change  in  the  amplitude  or  potential  of  the  waves 
is  when  they  are  modified  by  means  of  a  telegraph  key  to 
form  the  dots  and  dashes  of  the  telegraph  code,  by  means 
of  a  buzzer  to  give  what  is  known  as  modulated  C.  W., 
or  by  the  voice  modulations  for  radio  telephony. 

The  Vacuum  Tube  in  a  Transmitting  Role 

Thanks  to  the  recent  development  of  the  vacuum  tube 
as    a   generator   of   high   frequency   oscillations,    it   now 


230  RADIO  FOR  EVERYBODY 

becomes  possible  to  produce  continuous  oscillations  or  CW 
on  a  small  as  well  as  large  scale.  This  fact  has  resulted 
in  the  production  of  compact,  continuous  wave  transmit- 
ters which  may  be  used  for  radio  telephony  or  radio 
telegraphy  by  the  amateur.  In  fact,  at  this  writing  the 
CW  transmitters  now  being  offered  are  no  more  compli- 
cated in  their  operation  than  the  receiving  sets ;  in  truth, 
at  a  glance  one  could  not  tell  a  small  CW  transmitter  apart 
from  a  vacuum  tube  receiving  set. 

Let  us  consider  a  typical  radio  telephone  and  telegraph 
transmitter  now  on  the  market.  All  the  controls  and 
apparatus  necessary  to  operate  this  transmitter  are  mounted 
on  two  panels,  each  measuring  9  inches  by  4^  inches. 
The  left  panel  contains  the  grid,  plate,  and  the  antenna 
inductances  and  their  control  switches ;  a  compact  induc- 
tance unit  serving  as  a  choke  coil ;  a  send-receive  transfer 
switch;  and  variable  antenna  condenser.  The  right-hand 
panel  contains  tube  receptacles,  standard  modulation  trans- 
former, filament  rheostat,  radiation  ammeter,  grid  leak, 
grid  stopping  condenser,  and  filament  insulating  condenser. 
These  various  terms  will  become  clearer  as  we  read  more 
about  the  elements  of  a  CW  transmitter. 

Using  a  100-volt  "B"  battery  on  the  plates,  this  set 
radiates  .1  to  .2  ampere  and  the  range  is  10  to  15  miles. 
With  350  volts  impressed  on  the  plates  .3  to  .4  ampere  will 
be  radiated,  giving  a  range  of  25  to  30  miles.  With  500 
volts  plate  voltage,  the  aerial  ammeter  reading  will  be 
.5  to  .6  ampere,  or  sufficient  to  cover  35  to  50  miles. 

By  the  addition  of  a  buzzer  and  key,  modulated  con- 
tinuous wave  transmission  is  possible  and  the  above  ranges, 
which  are  for  the  radio-phone,  are  doubled.  Adding  a 
key  only,  provides  continuous  wave  communication,  trip- 
ling the  ranges.  However,  with  the  key  only,  the  waves 
are  absolutely  continuous,  or  what  is  known  as  straight 
C  W,  and  do  not  serve  quite  as  well  for  amateur  purposes 
as  the  interrupted  or  modulated  CW,  which  may  be  de- 
tected with  any  type  of  receiving  set  within  range.  The 
straight  .continuous   wave   can   only   be    detected   with   a 


«  3 

5-* 

►"« 

s  o 
X  a 
►s  S". 

c  p 

is 


^;2 

e.3 


3" 


&»' 


o* 


■O-d   OB 


t  O 
P   1   SO 
3  -»  ^ 

3D    •    1 

i.i§ 

-:S3 


tt 

' 

i 

^ 

o 
< 

z 

§ 

o 

0) 

n 
> 

i 

Ik       c   ^HHh 

hb 

^ 

>• 
o 

» 

V      2  '  i    ~fl 

■ 

u£' 

c 

\      >^    "JflH 

Eb 

lii« 

i 

? 

^     W 

H 

^ 

c 

05 

3} 

,  ^s^Cn             ^9 

kS 

^,^ 

"~~~~~^->w 

,illiaj| 

||i|L 

rS^S^  ,1    ■  IbB 

pll 

/^ 

J 

■ 

s 

^H^gi.     Jh 

H, 

1^^ 

i 

I 

ffl^srf 

■B^^^t       ll 

sgB 

^?  y  -- 

..._--„  J 

1 

HK 

r^^^w 

H 

l^^gM'     ,aB 

■H 

^R^' 

■ 

I^H 

^      ^ 

JHB 

^M 

1 

p  "^ 

3! 

1| 

Q 

P" 

jMBfj 

BB^^^^^ri 

|^fc'~ 

~ 

5 

^^^H 

|i|i|il|yi|['      (ft  wk 

K 

f  ~- 

^^^^K 

■    \i 

1 

1^ 

^u 

-1 

^--^ 

V 

■^^K$                          'W 

H 

ff^ 

^M^B^^^M 

i-'- 

\  '       >  r  r, 

-W^* 

fBmi'::'  4     %4 

P 

^tt 

I'^^^^p 

1 

-     a;  >  T 

K  1  1 

1 

% 

ipx,^  i 

X 

'^, 

,*f->^ 

M-j—y^                     ^              ft 

■ 

^B 

B       ^ 

-_i 

O  JB 

1 

B 

\ 

n 
n 

■0 

^V^^^HE 

IE 

9H|H 

pl     !^ 

2; 

i       ,.^,_' 

^^^B  ^S^^SB^s 

wH| 

IB§pB|^^p 

H 

'j 

^BH^^^ffia^^^H 

1^.  J 

i^^^^EB 

1            — 

z 

;                        - 

SBH^S^hI 

■n 

^HMpfm 

^                        ? 

B^B^^kB^^S 

ttH 

|^HH|^^^ 

^'                -        1 

E^^^^HB^HHHj 

I^BI 

■nf^K[^Wft^ 

Z     ; 

■ 

1 

n 

2  -i 

: 

' 

^^^^^^^^^^^^H 

^^H 

wB/B^^m. 

<£ 

^^^^^H 

H 

W^^m 

«^ 

^m 

1 

n 

^-^^p^BB 

B 

HH 

1 

232  RADIO  FOR  EVERYBODY 

receiving  set  intended  for  and  adjusted  for  continuous 
wave  reception,  as  explained  in  previous  chapters  dealing 
v^ith  receiving  sets. 

A  six-volt  storage  battery  lights  the  filaments  and  pro- 
vides current  for  the  microphone,  while  the  plate  current 
can  be  o'btained  from  a  rectifier  unit  and  transformer 
operating  on  alternating  current  supply,  or  any  motor- 
generator  set.  Any  manufacturer  of  radio-phone  trans- 
mitters will  explain  just  what  equipment  and  accessories 
are  required  for  this  kind  of  work.  It  is  too  involved 
to  be  treated  in  this  popular  work. 

Then  there  are  the  larger  types  of  radio-phone  trans- 
mitters. A  relatively  simple  cabinet  set,  with  a  panel 
measuring  13  inches  by  11^  inches,  and  8  inches  deep, 
may  be  relied  upon  for  uninterrupted,  dependable  trans- 
mission over  distances  up  to  60  miles.  Variable  controls 
have  been  reduced  to  a  minimum  and  operation  could  not 
be  further  simplified  in  many  of  the  ofiferings  of  this  class. 
On  the  face  of  the  panel  are  the  plate  current  milli-am- 
pere  radiation  meter,  two  filament  rheostat  knobs,  the 
send-receive  switch,  a  switch  for  changing  from  speech  to 
modulated  CW  or  straight  CW,  antenna  condenser  switch 
and  motor  control  switch.  On  the  rear  of  the  panel  are 
filter  condenser,  constant  current  coil,  high  frequency 
choke  coils,  grid  condenser,  plate  condenser,  filament  in- 
sulating condenser,  antenna  condenser,  grid  leak,  four  tube 
receptacles,  modulation  transformer,  antenna  inductance, 
and  microphone  resistance. 

To  supply  the  plates  with  a  potential  of  350  to  500 
volts,  a  32  or  110-volt  dynamotor  (a  single  motor  and 
generator  tmit)  or  a  32  or  110-volt  motor-generator  (a 
motor  and  a  generator  connected  together)  is  required, 
while  for  the  filaments  and  microphone  a  10-volt  storage 
battery  is  necessary.  The  32-volt  potential  is  mentioned 
because  certain  rural  districts  make  use  of  this  low  voltage 
in  their  isolated  plants  that  siipply  lighting  current. 

So  much  for  the  complete  sets  of  low  and  moderate 
power.  When  it  comes  to  more  ambitious  ranges,  running 
into  the  hundreds  of   miles,  a  much  larger   transmitter 


RADIO  FOR  EVERYBODY 


233 


must  be  considered.  Following  the  panel  idea,  there  are 
one-half,  one-kilowatt,  two-kilowatt,  and  larger  CW 
telegraph  and  telephone  transmitters.  The  various  con- 
trols and  meters  are  mounted  on  the  panel,  while  the 
various  components  are  mounted  at  the  rear,  both  on  the 
reverse  side  of  the  panel  and  on  iron  brackets  and  shelves. 

Why  CW  is  Popular 

In  time  it  is  believed  that  virtually  all  radio  amateur 
stations  and,  for  that  matter,  commercial  stations,  will 
be  using  CW  or  undamped  wave  transmitters  for  these 
reasons : 


Typical     radio-phone    transmitter,     which     is     provided     with 

rectifying  tubes   so  that  it   can  be  operated  on.  an  alternating: 

current     lighting:     circuit. 

(1)  Radio  telephony  is  made  possible  on  a  small  or 
large  scale.  (2)  Extremely  sharp  tuning  is  obtained  and 
consequent  reduction  of  interference  between  stations 
working  close  together.     A  slight  change  of  adjustment 


234 


RADIO  FOR  EVERYBODY 


Typical  CW  transmitting  equipment,  showing:  its  simplicity. 
The  coil  at  the  left  is  a  grid  coil,  while  the  instrument  at 
the  right  is  a  transmitting  helix,  made  up  of  a  number 
of  turns  of  flat  copper  strip.  The  clips  are  for  the  purpose 
of  making  the  necessary  connections  at  any  points ,  on  the 
helix   in   order   to   obtain   the   proper   wave   length   values. 

throws  a  receiver  out  of  tune,  and  the  operator  may  pass 
over  the  correct  tuning  point  by  too  rapid  a  movement  of 
the  adjusting  knobs,  so  sharp  is  the  continuous  v^ave 
transmitter.  (3)  Since  the  oscillations  go  on  continuously 
instead  of  only  a  small  fraction  of  the  time,  as  in  the 
case  of  damped  waves,  their  amplitudes  need  not  be  so 
great  and  hence  the  voltage  applied  to  the  transmitting 
condenser  and  aerial  are  much  lower.  This  means  that 
the  problem  of  installation  is  reduced  to  a  minimum  and 
the  installation  of  such  a  set  is  made  relatively  simple. 
(4)  With  damped  waves  the  pitch  or  tone  of  received 
signals  depends  wholly  upon  the  number  of  sparks  per 
second  at  the  transmitter.  With  undamped  or  continuous 
-waves  the  receiving  operator  controls  the  tone  of  the  re- 
ceived signals,  and  this  can  be  varied  and  made  as  high  or 
as  low  as  possible  in  pitch  to  distinguish  the  signals  from 


RADIO  FOR  EVERYBODY 


235 


atmospheric  disturbances  and  to  suit  the  pitch  to  the 
operator's  ears  and  to  the  sensitiveness  of  the  telephone 
receivers.  These  advantages,  freedom  from  interference 
caused  by  other  stations,  the  use  of  high  tones  and  low 
vokages,  and  the  greater  freedom  from  strays  combine  to 
permit  a  higher  speed  of  telegraphy  than  could  otherwise 
be  obtained. 

How  CW  Transmitters  Work 

Persistent,  continuous  or  undamped  waves,  whichever 
you  wish  to  call  them,  can  be  generated  by  several  distinct 
methods,  each  having  its  advantages  and  disadvantages,  as 
follows : 

(1)  The  arc  or  Poulsen  method,  so  named  after  its 
Danish   inventor.      Oscillations   of    radio    frequency   are 


A   50-watt   transmitting    tube,    showing^   its    principal   elements. 

Like  the  amplifier  and  detector  tubes,  it  comprises  a  filament, 

grid,    and    plate. 


336  RADIO  FOR  EVERYBODY 

obtained  by  means  of  an  electric  arc  burning  in  an  atmos- 
phere of  hydrogen  and  in  a  strong  magnetic  field.  The 
arc  method  produces  undamped  waves  of  rather  long  wave 
length,  and  is  ordinarily  operated  on  500  volts  direct  cur- 
rent. It  has  been  discovered  that  an  electric  arc  between 
proper  electrodes,  shunted  by  an  inductance  and  a  con- 
denser, will  produce  continuous  oscillations  through  the 
shunt  circuit,  and  such  a  circuit  is  used  to  excite  an  aerial 
circuit  for  transmitting  purposes.  Depending  on  whether 
a  telephone  microphone  or  key  is  employed,  the  arc  gen- 
erator may  be  arranged  for  radio  telephony  or  telegraphy. 
Needless  to  say,  the  arc  is  unsuitable  in  many  ways  for 
amateur  radio  purposes,  because  it  is  too  elaborate  to 
begin  with,  the  oscillations  are  of  too  great  a  wave  length, 
and  the  arc  cannot  be  constructed  for  small  powers  yet 
produce  efficient  results. 

(2)  The  high  frequency  alternator  method,  which  is 
practically  an  alternating  current  generator  of  special  de- 
sign having  a  great  number  of  poles  revolving  at  a  high 
speed,  in  order  to  obtain  the  necessary  high  frequency. 
A  standard  General  Electric  Company  two-kilowatt  high 
frequency  alternator  designed  for  a  frequency  of  200,000 
cycles  or  1,500  meters  wave  length  must  be  revolved  at  a 
speed  of  20,000  revolutions  per  minute.  This  is  a  very 
high  rate  of  speed.  Imagine  a  speed  seven  or  more  times 
as  fast  as  the  turning  of  the  average  electric  fan !  Again, 
needless  to  say,  this  is  not  a  good  method  for  the  average 
amateur. 

Skipping  over  several  other  highly  technical  methods, 
we  come  to  the  vacuum  tube  oscillator  method,  which  is 
brought  about  by  using  what  is  known  as  the  Armstrong 
"feed  back"  or  regenerative  system,  which  has  already 
made  our  acquaintance  in  the  previous  chapters  dealing 
with  receiving  systems  and  methods.  This  kind  of  €W 
transmission  is  brought  about  by  placing  an  inductance 
in  series  with  the  plate,  and  this,  in  turn,  is  placed  in 
inductive  relation  with  the  grid,  causing  the  plate  current 
to  act  on  the  grid  and  producing  oscillations  of  a  frequency 


^38 


RADIO  FOR  EVERYBODY 


dependent  entirely  on  the  constants  or  electrical  values  of 
the  circuit.  Perhaps  the  accompanying  diagram  makes 
the  foregoing  description  clearer.  It  will  be  noted  that  the 
arrangement  here  shown  is  very  mUch  like  the  usual  regen- 
erative receiving  hook-up,  except  that  the  telephone  re- 
ceivers have  been  left  out,  and  a  telegraph  key  is  placed 
in  the  primary  circuit  of  the  oscillation  transformer  or 


-S-B 


rr 


vc, 


n  G 


Simple  CW  telegraph  transmitter  which 
may  be  assembled  by  any  one.  A — aerial; 
G — grround;  P  and  S>^primary  and  sec- 
ondary of  the  loose-coupler  LC;  VCl — 
variable  condenser  for  reducing  wave 
length  of  aerial-ground  circuit  if  neces- 
sary; VC2 — variable  condenser;  OT — oscil- 
lating tube;  A — filament  battery;  K — fila- 
ment rheostat;  B — filament  battery;  F— 
feed-back    or    tickler    eoil. 


transmitting  loose-coupler  in  such  a  manner  as  to  short- 
circuit  several  turns  every  time  it  is  pressed  down.  This 
causes  the  wave  length  to  fluctuate,  and  produced  the  dots 
and  dashes  in  the  sharply  tuned  continuous  waves  inter- 
cepted at  the  receiving  end. 

The  experimenter  is  practically  limited  to  the  vacuum 
tube  for  his  experiments  and  work  with  undamped  waves 
because  of  the  cost  and  other  deterrent  features  of  other 


VACUUM    TUBES 


INDUCTANCE 
UNIT 


WAVE     t.ENGTH 
'CHANGiNG 
GEAR 


POWER 
CONTROLS 


Mechanism*  of  a  commercial   CW   telegrraph   transmitter,   using^ 

several  50-watt  tubes  and  a  chopper  for  producing  modulated 

continuous   waves. 


240 


RADIO  FOR  EVERYBODY 


systems.  Even  leaving  aside  the  consideration  of  cost, 
in  most  instances  the  undamped  wave  generators  other 
than  the  vacuum  tube  operate  best  on  long  wave  lengths 
which  are  barred  to  the  amateurs.  However,  the  fact 
remains  that  the  vacuum  tube  makes  an  excellent  generator 
— one  that  is  quite  flexible,  too,  since  its  power  can  be 
increased  merely  by  connecting  more  bulbs  in  parallel. 

Placing  the  key  across  a  few  turns  of  the  oscillation 

transformer,   so  that  the  CW  transmitter  is   tuned  and 

r-T-T  detuned    with    the 

V  A  ^ l|l|lH^^lKn 


1. 


^  1 1     333=         operation  of  the  key, 
I  I     ^^  often  done.     It  will 

Uoooo,,..^.^_J     be    recalled    that    the 

sharpness     of     u  n  - 

damped  waves  is  quite 
__  marked  at  the  receiv- 
J  5  ing  end,  so  that  it  fol- 
J  lows  that  when  the  set 
~  is  detuned,  even  to 
the  extent  of  two 
turns  of  the  secondary 

Simple    method    of    produciiiF     ^  ^        ^  ^  C        OSCillatioU 


buzzer  modulated  CW  waves,   transformer    the 

Note     the     buzzer     Inductively  ' 

connected  with  the  grid  cir- 
cuit. A — aerial;  VCl — vari- 
able condenser  in  aerial- 
ground  circuit;  VC2 — vari- 
able condenser  in  oscillating 
circuit ;  R — filament  rheostat ; 
A. — filament  battery ;  B — plate 
battery. 


waves  are  not  heard 
at  that  moment.  In 
this  manner  it  is  pos- 
sible to  make  dots  and 
dashes  with  an  or- 
dinary* telegraph  key 
even  when  handling  considerable  transmitting  power,  since 
little  power  is  broken  by  the  contacts. 

Another  method  of  CW  transmission  is  to  use  mod- 
ulated persistent  waves  by  having  a  transformer  in  the 
grid  circuit  and  a  buzzer  and  key  in  the  primary  winding 
of  same,  as  shown  in  the  accompanying  diagram.  The 
note  emitted  is  similar  to  the  tone  of  the  buzzer  used,  and 
such  signals  can  be  received  on  any  type  of  receiving  set 
as    distinguished    from    the    straight    CW    waves    which 


RADIO  FOR  EVERYBODY  241 

cannot  be  heard  with  the  ordinary  crystal  detector  working 
in  a  damped  wave  receiving  circuit. 

What  is  known  as  a  chopper  is  also  used  to  break  up 
the  continuous  waves  in  order  to  make  them  audible  with 
any  type  of  receiving  set.  The  chopper  is  simply  a  motor- 
driven  commutator  or  circuit  breaking  device,  which  breaks 
a  circuit  a  given  number  of  times  according  to  the  speed 
at  which  it  is  revolved.  The  chopper  can  be  placed  in 
series  with  the  grid  resistance  and  its  rate  oi  rotation  will 
then  determine  the  note  of  the  CW  signals,  and  make  them 
audible  to  any  receiving  set. 

The  matter  of  the  aerial  is  a  very  important  consider- 
ation in  CW  transmission,  for  the  reason  that  the  waves 
are  so  sharply  tuned  that  the  slightest  change  in  wave 
length  affects  the  reception  of  the  waves.  Thus  if  the 
aerial  should  sway  with  the  wind  and  change  the  distance 
between  its  wires  and  the  ground,  the  wave  length  of  the 
transmitted  waves  will  also  be  varied,  ever  so  slightly  to 
be  sure,  but  enough  to  give  some  trouble  at  the  receiving 
end. 

For  this  reason  special  aerials  are  often  used  in  C  W 
transmission.  Instead  of  using  the  flat-top  aerial,  with 
the  wires  side  by  side  supported  on  spreaders  at  either 
end,  the  cage  type  of  aerial  is  often  employed.  This 
aerial  has  hoops  or  rings  at  each  end  instead  of  the  usual 
spreaders,  and  the  wires  are  arranged  on  these  hoops  or 
rings  so  as  to  form  a  round  or  cage-like  aerial  which  is 
supported  in  the  usual  manner.  The  cage  type  of  aerial 
is  more  constant  in  its  electrical  characteristics  and  is 
therefore  more  satisfactory  in  CW  work.  Furthermore, 
to  ensure  still  greater  rigidness,  the  counterpoise  form 
of  ground  is  also  employed  to  a  large  extent  in  CW  trans- 
mission. 

The  necessity  for  a  rigid  aerial  system  is,  obviously, 
more  essential  when  the  dots  and  dashes  or  the  telephone 
modulation  is  obtained  through  a  change  in  wave  length, 
than  w^hen  the  dots  and  dashes  and  telephone  modula- 
tion are  caused  by  a  change  in  amphtude  or  voltage. 


24^ 


RADIO  FOR  EVERYBODY 


pHBi  iiiiif ,- ww» 

1 

■■Iiiiii 

■^iil 

1 

mmBims-  '•:=! 

1 

wiiiltililiSffliiWil^           ■«*■:-  ■  ■  - 1: 

I 

^■:fa*:-^e--^-iyv  smmm 'imsmmmemm liiiiaMps                   ..i 

^Bliiiiii^^                             ■-,  . 

CW  telegraph  and  radio-phone  transmitter   of  the   panel   type, 

with    the    various    controls    and    meters    mounted    on    the    front 

face.     Transmitters   of  this   type   are  being   used   in   several  of 

the    radio-phone    broadcasting    stations. 

The  general  subject  of  CW  transmitters  is  such  a  large 
one  that  we  cannot  afford  to  go  deeper  into  it  at  this  time. 
Then  again,  it  is  very  well  covered  by  more  advanced 
works,  and  certain  radio  companies  have  brought  out  ex- 


RADIO  FOR  EVERYBODY 


243 


ceptionally  complete  and  explicit  literature  on  CW  trans- 
mission. 

Radio  Telephony  Reduced  to  its  Simplest  Form 

If  one  is  satisfied  with  a  range  of  but  a  few  miles,  a  CW 
transmitter  may  be  readily  assembled,  and  it  can  be  almost 
as  easily  used  for  radio-phone  work  as  for  radio  telegraph. 

First  of  all,  the  radio  amateur  must  obtain  the  proper 
vacuum  tube.  So  far  we  have  spoken  of  the  vacuum 
tube  detector  and  the  vacuum  tube  ampUfier  tubes,  but 
now  we  come  to  the 
transmitting  tubes. 
The  standard  trans- 
mitting tubes  now 
available  on  the  mar- 
ket come  in  5-watt, 
50- watt  and  2 50- watt 
sizes.  For  our  pres- 
ent purpose  the  5- 
watt  is  the  most  pop- 
ular, since  we  are 
dealing  with  low 
power.  Two  5-watt 
tubes  in  parallel  will 
put  from  one  and 
one-quarter  to  one 
and  three-quarter  am- 
peres in  the  amateur's 
aerial.  Using  one  of 
these  tubes  as  a  mod- 
ulator and  the  other 
as  an  oscillator,  for 
experimental  radio 
telephony,  distances 
up  to  40  miles  can  be 
covered,  and  at  least  four  times  that  distance  when  the 
two  tubes  are  connected  in  parallel  for  CW  telegraphy. 
Four  or  five  5-watt  tubes  can  be  worked  in  parallel  with 
increased  range.    The  5-watt  tubes  are  also  used  as  power 


B 


Hlllll-VSAW 
A         ^ 


A  simple  continuous  wave  telegraph 
transmitter,  making:  use  of  a  single 
5-watt  tube.  This  set  transmits 
straight  CW.  A — aerial;  I — aerial  in- 
ductance; B — high  voltage  battery; 
VCl — variable  condenser;  G — ground; 
K — telegraph  key;  VC2 — grid  conden- 
ser; OT — oscillating  tube;  A — filament 
battery ;    K — filament   rheostat. 


244 


RADIO  FOR  EVERYBODY 


amplifiers  in  radio  receiving  circuits.  The  energy  ampli- 
fication obtained  therefrom  is  particularly  useful  for  the 
operation  of  loud-speakers. 

The  50-watt  transmitting  tube  is  intended  for 

\  /     long-distance  telephony  and  telegraphy.     Two 

^A    50-watt   tubes    connected    in   a   self-rectifying 

or  in  a  straight  direct-cur- 
rent  plate   excitation   cir- 
cuit will   give  aerial  cur- 
rents of  three  to  four  am- 
peres   at    amateur    wave 
lengths.      A    single    tube 
operated    from    a    direct- 
current  source  or  a  recti- 
fied   alternating    cur- 
rent   source    will    put 
two    and    a    half    to 
three   amperes   in  the 
amateur's     aerial. 
Hundreds     of      these 
tubes    are    already    in 

Simple     combination  •  ,  . 

radio  telegraph  and  usc  m  amatcur  trans- 

radio-phone      trans-  mittingf          S  t  a  t  i  O  n  S 

mitter.         A — aerial;  ^             S                 , 

I— aerial  inductance ;  thrOUghoUt     the    COUU- 

^n    b       B— higrh-voltage  bat-  ^                 j     Hic;tpnrp«;    nn 

tery;     VCl— variable  ^^J'    ^"*^    QlSianceS    Up 

condenser;     TR — telephone    microphone;  tO      1  900      mileS      have 

VC2 — variable    condenser;    K — telegraph  -,             '                 j    •, 

key;    OT— oscillating    tube;    A— filament  been  COVercd    by  USmg 

battery;     K— filament    rheostat.  {^    ^n    appropriate    OS- 

cillating  circuit. 

The  250-watt  tube  is  the  most  powerful  tube  of  the 
series  now  on  the  market  for  experimental  and  general 
transmission  purposes.  This  tube  is  equipped  with  a  spe- 
cial filament  which  gives  exceptionally  long  operating  life. 

Let  us  return  to  the  5-watt  tube  and  to  the  simple  trans- 
mitter, which  is  more  in  the  province  of  this  book  than 
the  more  powerful,  more  elaborate  transmitters.  A  simple 
radio-phone  transmitter  may  be  readily  built  or  rather 
assembled  by  the  radio   enthusiast,  who  wishes  to  do  a 


TR  NX 


rr 


RADIO  FOR  EVERYBODY 


245 


little  talking  on  his  mvn  account  and  is  willing  and  ready 
to  secure  his  operator's  and  station  licenses. 

The  first  step  is  to  obtain  a  5-watt  transmitting  tube. 
Then  we  need  two  22^ -volt  B  battery  of  the  same  kind 
as  we  used  for  the  receiving  sets.  On  one  battery  a  5- 
watt  tube,  under  good  conditions,  will  transmit  5  to  10 
miles.  Then  we  need  a  variable  condenser  of  0.001  mfd. 
maximum  capacity,  which  is  connected  in  the  ground  cir- 
cuit, and  another  variable  condenser  with  a  maximum 
capacity  of  0.0005  mfd.  which  is  placed  in  the  grid  circuit. 
A  suitable  CW  helix  or  inductance  is  also  required.  This 
last-named  piece  of  apparatus  may  be  purchased  already 
made,  or  it  can  be  constructed  of  heavy  copper  wire  made 
into  a  coil  with  the  turns  separated  ^4  to  }4  inch  apart. 
Clips  are  used  to  make  connections  with  any  desired  part 
of  the  helix  or  inductance.  A  six-volt  storage  battery, 
vacuum  tube  socket,  filament  rheostat,  and  a 
\  I  /  telegraph  key  complete  the  outfit.  A  micro- 
\/a  phone  can  be  substituted  for  the  key  and  the 
set  converted  into  a  short-distance  telephone 
transmitter.  If  possible,  a  hot  wire  ammeter 
should  also  be  included 
with  the  set.  This  instru- 
ment is  placed  in  the 
ground  lead  and  serves  to 


8:=: 


How  two   or  three  tubes  may  be  arranged 

in     parallel    for     obtaining     greater     power 

while  still  using  the  same   simple  arrange- 

G       ment.     In  this  case   straight   CW  telegraph 

is  obtained. 


246  RADIO  FOR  EVERYBODY 

indicate  when  the  transmitter  is  adjusted  to  maximum 
efficiency. 

Tuning  the  set  is  accompHshed  in  very  much  the  same 
manner  as  with  the  damped  wave  transmitter.  With  the 
filament  of  the  tuhe  Hghted  and  the  set  oscillating  properly, 
the  series  and  the  grid  condensers  are  varied  until  a  max- 
imum output  is  indicated  by  the  ammeter.  However, 
this  method  does  not  indicate  just  what  the  wave  length 
may  be,  and  one  may  be  overstepping  the  200-meter  limit. 
It  may  be  well  to  have  nearby  amateurs  listen  in  and  say 
whether  the  emitted  wave  appears  to  be  below  200  meters, 
and  also  when  the  transmission  is  at  its  best. 

The  output  of  the  transmitter  can  be  increased  by  using 
a  higher  voltage  on  -the  plate.  By  means  of  additional 
B  battery  units,  the  voltage  can  be  increased  to  90  volts. 
It  must  be  remembered  in  this  connection  that  the  energy 
for  the  waves  is  taken  from  that  source.  Just  so  long  as 
the  tube  does  not  glow  with  a  blue  haze,  the  B  battery 
voltage  can  be  piled  on,  increasing  the  efficiency  and  the 
range.  Another  scheme  is  to  use  two  or  three  tubes  in 
parallel,  with  the  grids  connected  together  and  also  the 
plates.     Only  one  B  battery  is  required  for  all  the  tubes. 

Much  could  be  said  here  regarding  modulator  tubes, 
which  permit  of  modulating  heavy  transmitting  currents 
by  means  of  ordinary  carbon  microphones  through  the 
medium  of  vacuum  tubes  known  as  modulator  tubes,  and 
magnetic  modulators.  Then  there  are  filter  reactors,  rec- 
tifiers, filters,  microphone  transformers,  and  other  devices 
which  enter  into  the  more  elaborate  CW  transmitters,  but 
for  further  information  along  these  lines  we  must  look 
to  more  advanced  works  specializing  in  CW  transmission. 


Chapter  IX. 

THE  UNUSUAL   USES   OF   RADIO   ON 
LAND  AND  SEA  AND  IN  THE  AIR 


RADIO  has  many  uses  aside  from  the  broadcasting  of 
entertainment  and  news  and  the  Unking  of  widely 
separated  points.  In  fact,  it  seems  as  though  we  have 
done  httle  more  than  scratch  the  surface  of  its  vast  pos- 
sibiHties,  and  that  the  inventive  talent  of  today  must  lead 
us  to  still  greater  and  more  startling  achievements  in  the 
application  of  radio. 

In  the  early  days  of  radio,  too  much  was  expected  of  it. 
There  was  much  promise  of  the  transmission  of  power 
by  radio  in  order  that  airships  and  automobiles  and  street 
cars  and  ocean  liners  might  be  operated  by  distant  power 
plants  without  the  agency  of  wires  or  cables.  Yet  we 
know  today  that  the  transmission  of  power  by  radio  is  still 
a  remote  possibility ;  we  know  that,  starting  with  one  kilo- 
watt at  the  transmitting  end,  we  obtain  less  than  a  thou- 
sandth of  a  watt,  or  one  millionth  of  the  original  power 
expended  at  the  receiving  end.  .  The  radio  method  of 
transmitting  power  is  a  most  inefficient  one,  and  only  if 
we  hit  upon  some  entirely  new  principle  of  transmission 
and  reception  can  we  hope  to  make  anything  of  the  idea 
of  radio  transmission  of  power. 

However,  whatever  radio  wonders  may  have  been  ex- 
pected in  the  early  days  have  been  more  than  realized, 
even  though  the  present  achievements  may  be  along  en- 
tirely different  lines. 


248  RADIO  FOR  EVERYBODY 

The  Marvels  of  Radio  Control 

One  of  the  most  promising  fields  of  unusual  radio,  if 
we  may  call  it  such,  is  the  one  given  the  broad  name  of 
radio  control.  This  means  the  controlling  of  machinery 
and  other  things  at  a  distance  through  the  use  of  radio. 
Thus  small  vehicles  and  boats  controlled  by  radio  have 
attracted  no  little  attention  wherever  they  have  been 
shown. 

Mysterious  as  these  things  may  be,  there  is  really 
nothing  very  complicated  about  them.  This  does  not  mean 
to  say  that  anyone  can  construct  a  successful  radio-  con- 
trolled car  or  boat  with  little  trouble,  because  there  is 
a  good  deal  of  experimental  work  to  be  performed  before 
such  a  delicate  assembly  can  be  made  to  work  properly; 
but  the  principles  are  public  property  and  may  be  em- 
ployed by  anyone  of  an  inventive  turn  of  mind. 

The  principle  of  radio  control  rests  on  the  transmission 
of  certain  signals  or  radio  waves  which  affect  a  detector 
in  the  same  manner  as  the  usual  receiving  set.  Instead  of 
rectifying  the  intercepted  wave  energy  "for  a  pair  of  tele- 
phone receivers  or  for  a  loud-talker,  however,  the  detector 
in  this  case  passes  its  output  over  to  a  delicate  relay, 
which  is  a  device  that  is  actuated  by  a  source  of  delicate 
current  so  as  to  open  and  close  the  circuit  of  a  more 
powerful  local  current.  The  more  powerful  current  can 
therefore  be  made  to  do  whatever  work  is  desired.  So,  if 
we  press  the  key  of  a  transmitter,  tuned  to  the  right 
wave  length,  the  machinery  to  be  controlled  intercepts 
the  signal  and  operates  its  relay,  which  in  turn  closes  the 
local  current  circuit  for  the  performing  of  any  desired 
task.  However,  such  a  simple  system  gives  only  one  com- 
mand, so  to  speak,  and  since  a  number  of  different  tasks, 
must  be  commanded  by  means  of  the  remote  control,  some 
other  agency  must  be  introduced  of  multiplying  the  num- 
ber of  commands  that  can  be  issued. 

There  are  several  ways  in  which  a  number  of  different 
things  can  be  commanded  or  controlled  by  remote  control.. 
The  simplest  method  is  to  use  a  revolving  contact  drum,. 


\ 

■■»- 

1 

L *.  1^ 

J^ 

1^ 

250  RADIO  FOR  EVERYBODY 

as  it  is  termed,  on  which  are  arranged  metal  strips  which 
can  make  various  combinations  of  electrical  connections 
and  which  come  into  action  one  by  one  as  the  drum  is 
revolved.  This  drum  is  revolved  continuously  at  a  pre- 
determined speed,  or  step  by  step.  In  the  latter  case  one 
combination  of  connections  after  another  is  brought  into 
action  by  means  of  an  electro-magnetically  operated 
ratchet  device,  which  functions  through  the  closing  of  the 
relay  contacts.  Every  time  a  signal  is  sent  out  by  the 
transmitter,  the  relay  of  the  receiving  device  closes  the 
circuit,  current  is  sent  through  the  combination  that  hap- 
pens to  be  effective  at  that  moment,  and  the  drum  is 
then  given  a  one-step  turn  to  the  next  combination  as  the 
signal  stops.  The  next  signal  sent  through  repeats  the 
same  performance,  but  with  the  combination  then  effec- 
tive being  used. 

Now  the  combinations  can  be  arranged  to  do  all  kinds 
of  different  things.  Supposing  we  are  dealing  with  a 
model  submarine,  controlled  by  radio.  The  first  combina- 
tion on  the  drum  starts  the  motors ;  the  second  steers  the 
craft  to  the  left;  the  third  brings  the  rudder  to  the  nor- 
mal position;  the  fourth  steers  to  the  right;  the  fifth 
causes  the  driving  motors  to  drop  to  half  speed ;  the  sixth 
deflects  the  diving  rudders  so  that  the  craft  submerges; 
the  seventh  brings  the  craft  back  to  the  surface  again;  the 
eighth  stops  the  motors. 

But  supposing  we  want  the  craft  to  steer  to  the  right, 
when  the  combination  then  effective  is  the  seventh,  or 
the  one  that  brings  it  back  to  the  surface,  what  then? 
Simple  enough.  We  simply  send  out  one  short  snappy 
signal  after  another  without  appreciable  pause  between 
them,  so  that  the  craft  does  not  have  time  to  respond  to 
any  one  of  the  controls,  brought  into  play  in  rapid  suc- 
cession until  we  reach  the  desired  control,  when  we  stop 
and  the  craft  obeys.  Generally,  some  indication  is  pro- 
vided so  as  to  show  just  what  combination  happens  to 
be  operative  at  any  given  moment.  Little  colored  lights 
can  be  used  to  indicate  when  the  start  of  a  cycle  of  com- 
binations is  at  hand,  and  the  operator  knows  just  how 


252  RADIO  FOR  EVERYBODY 

many  signals  to  send  in  order  to  reach  the  desired  control. 
Another  method  is  to  use  a  steadily  revolving  drum 
aboard  the  vehicle  or  boat  to  be  controlled.  A  watch, 
carefully  synchronized  so  that  its  large  hand  will  turn  at 
the  same  speed  as  the  revolving  drum,  is  used  by  the 
operator.  In  this  manner  the  operator,  while  watching  his 
synchronized  indicator,  knows  just  the  right  moment  to 
press  the  key  in  order  to  take  advantage  of  any  desired 
conditions  for  any  desired  commanci. 

The  Radio  Compass  and  What  It  Means 

Something  has  been  said  regarding  the  use  of  loops 
for  receiving  purposes.  A  loop  consists  of  a  wooden 
frame  with  a  number  of  turns  of  wire.  The  loop  is 
used  in  the  same  manner  as  would  the  secondary  of  a 
coupler  in  a  receiving  circuit,  with  a  variable  condenser 
or  variometer  to  vary  its  wave  length.  No  ground  is 
employed.  The  loop  receives  signals  loudest  when  it  is 
pointing  end  on  towards  the  transmitting  station,  and  this 
fact  has  brought  the  radio  compass  into  existence. 

The  radio  compass  is  nothing  more  than  a  loop  receiv- 
ing set.  Thus  the  loop,  which  is  mounted  in  such  a 
manner  as  to  be  readily  swung  about  on  its  vertical  axis, 
is  orientated  until  signals  are  picked  up  and  a  line  can 
then  be  drawn  on  a  corresponding  map  to  indicate  the 
direction  from  which  the  signals  are  coming.  However, 
the  loop  indicates  only  the  general  line  along  which  the 
signals  are  being  received,  and  there  is  no  telling  whether 
they  come  from  one  end  of  the  loop  or  the  other.  How- 
ever, in  most  instances  the  operator  knows  whether  it  is 
in  one  direction  or  the  other,  and  he  only  requires  the 
directive  line. 

The  radio  compass  generally  consists  of  two  or  more 
radio  compass  stations  on  shore,  at  the  entrance  to  a 
harbor  or  some  other  point.  A  ship,  wishing  to  know 
its  exact  bearings,  calls  up  the  radio  compass  stations, 
and  these  stations,  by  orientating  their  loops,  secure  two 
directive  lines  for  the  ship.  Since  the  radio  compass  sta- 
tions are  located  a  certain  distance  apart,   forming  the 


RADIO  FOR  EVERYBODY 


253 


base  of  an  imaginary  triangle,  and  since  a  pair  of  stations 
obtain  an  angle  reading  formed  by  the  direction  of  the 
received  signals  and  <the  base  line,  it  is  a  simple  matter 
with  a  known  base 


me  and  two  angles  to  construct  an 


The   radio   compass   which   is   employed    as   an    aid  in   navigation.     A 

number    of  turns   of  wire  are   wound   about  the  large  wooden   frame 

which  is  rotatably   mounted  in   the   stationary  frame,  so  that  it  can 

be  orientated. 


254  RADIO  FOR  EVERYBODY 

imaginary  triangle,  the  apex  of  which  is  the  location  of  the 
ship.  The  radio  compass  stations  then  call  up  the  ship 
and  give  the  navigator  his  exact  position. 

During  the  war  the  radio  compass  was  employed  for 
locating  enemy  radio  transmitters.  The  Germans  em- 
ployed the  radio  compass  to  guide  their  Zeppelins  through 
the  blackness  of  the  night  in  their  raids  on  London  and 
Paris.  That  is  why  the  Zeppelin  flew  with  such  rare 
precision  over  enemy  territory  and  sea,  and  back  to  their 
flying  fields. 

More  recent  developments  in  the  radio  compass  have 
brought  about  a  simpler  method.  Now  the  loop  is  carried 
on  the  ship,  and  the  operator  obtains  directionab readings 
from  two  shore  stations  whose  locations  are  known,  so 
that  with  a  given  apex  angle  and  a  known  base  line,  it 
becomes  possible  to  reconstruct  an  imaginary  triangle  and 
to  determine  the  exact  position  of  the  ship. 

Wired  Wireless 

For  some  time  back  it  has  been  possible  simultaneously 
to  transmit  several  telegraph  messages  over  a  single  tele- 
graph circuit.  Also,  certain  attempts  have  been  made  to 
develop  a  system  of  tuned  or  syntonic  multiplex  tele- 
graphy. But  it  has  remained  for  the  man  who  is  at 
present  Chief  Signal  Officer  of  the  United  States  Army, 
Major  General  Squier,  to  develop  a  system  of  communi- 
cation known  as  wired  wireless,  which  makes  it  possible  to 
carry  on  as  many  as  ten  or  more  two-way  simultaneous 
telephone  conversations  over  one  electrical  circuit.  It 
was  in  1910  that  Major  General  Squier  (then  Major), 
by  a  bold  and  ingenious  adaptation  of  the  fundamental 
principles  and  apparatus  previously  employed  in  radio 
telegraphy  and  telephony,  developed  the  multiplex  sys- 
tem which  bears  his  name,  and  therefore  established  a 
distinct  branch  of  the  art  of  communication. 

The  fundamental  principle  of  the  Squier  system  is  the 
application  of  high  frequency  electrical  resonance,  or  tun- 
ing as  it  is  understood  in  radio  work,  to  wire  communi- 


256  RADIO  FOR  EVERYBODY 

cations.  Previous  attempts  to  solve  the  multiplex  prob- 
lem had  been  based  largely  on  electro-mechanical  reson- 
ance. The  system  employs  the  elements  of  the  radio 
telephone  installation,  the  essential  difference  being  that  in 
place  of  the  connections  to  earth  and  the  usual  antenna, 
we  have,  in  this  case,  connections  to  the  two  wires  con- 
stituting a  physical  pair.  The  two  fundamental  factors, 
then,  in  the  Squier  system  of  multiplex,  are  the  utilization 
of  electrical  resonance  and  the  use  of  a  receiving  device 
which  delivers  to  the  telephone  receiver  a  varying  undirec- 
tional  current  corresponding  to  the  voice  current  supplied 
to  the  modulating  device  at  the  transmitting  station. 
Whether  the  frequency  of  the  carrier  current  is  low  or 
high  does  not  modify  the  basic  principles  involved.  In 
this  system  electro-magnetic  waves  of  predetermined 
length  are  guided  by  the  metallic  circuit,  instead  of  radiat- 
ing in  all  directions  from  an  antenna.  While  there  un- 
doubtedly is  a  certain  amount  of  radiation  from  the  phy- 
sical line,  the  over-all  efficiency  of  the  guided- wave  sys- 
tem, as  wired  wireless  is  also  called,  is  obviously  materially 
higher  than  in  the  case  of  a  free-wave  system.  This  has 
been  thoroughly  confirmed  by  experience. 

It  is  reported  that  in  general,  guided-wave  transmis- 
sion gives  a  more  nearly  perfect  reproduction  of  the  voice 
than  does  wire  telephony.  In  ordinary  telephony  there 
are  three  inherent  causes  of  distortion,  to  wit:  the  micro- 
phone, the  telephone  receiver,  and  that  due  to  the  line. 
The  first  two  are,  of  course,  present  in  the  high  fre- 
quency system.  The  distortion  due  to  the  Hne  is,  how- 
ever,  absent. 

Another  important  aspect  of  communication  is  secrecy. 
When  used  as  a  direct  private  line  of  telephonic  com- 
munication, as  in  the  case  of  leased  lines  between  busi- 
ness houses  in  different  cities  or  for  press  work,  we 
have  in  this  method  a  system  of  communication  which  ac- 
cords a  high  degree  of  secrecy.  Common  experience  in- 
dicates how  little  real  privacy  obtains  when  employing  the 
ordinary  telephone.     While  radio  telephone  has  a  distinct 


258  RADIO  FOR  EVERYBODY 

and  very  important  field  in  communication  at  sea,  it  ob- 
viously has  serious  limitations  when  employed  for  strictly 
personal  and  business  purposes.  While  there  is  no  knov^n 
means  of  communication  v^^hich  cannot  be  tapped,  yet 
from  the  nature  of  the  system  direct  guided-v^ave  tele- 
phony possesses  the  greatest  element  of  secrecy  of  any 
•telephonic  means  of  communication,  according  to  Chas. 
A.  Culver,  Ph.D.,  to  whom  the  author  is  indebted  for 
these  facts  on  wired  wireless. 

Another  advantage  of  the  guided- wave  system  is  that 
communication  may  be  maintained  between  two  points 
when  the  physical  circuit  which  serves  as  a  guide  for  the 
high  frequency  waves  is  out  of  commission  for  ordinary 
telephone  service.  Both  wires  of  the  physical  pair  may 
be  cut,  the  line  short-circuited,  and  at  least  one  of  the 
wires  grounded  without  interrupting  communication  over 
the  super-channel.  This  has  been  repeatedly  demonstrated 
and  naturally  means  much  in  emergency  service  of  all 
kinds. 

Another  feature  to  be  noted  in  connection  with  guided- 
wave  telephony  is  the  flexibility  of  the  system.  When 
used  as  a  through  trunk  channel,  a  given  set  of  equip- 
ment may,  as  previously  indicated,  be  instantly  shifted 
from  one  physical  circuit  to  another.  Further,  the  en- 
tire guided-wave  equipment  may  be  quickly  transported 
from  one  point  on  a  physical  system  to  another,  thus 
making  it  possible  readily  to  increase  the  traffic-carrying 
capacity  of  the  lines  between  points  where  a  temporary 
congestion  exists,  due  to  seasonal  or  other  causes. 

Guided  wireless  is  but  another  achievement  of  modern 
radio — but  another  instance  of  how  radio  has  collaborated 
rather  than  fought  the  wire  telephone  and  telegraph,  as 
was  expected  of  it  in  the  early  days  of  the  art. 


Chapter  X. 

RADIO    IN   WORKING   CLOTHES,   OR 

THE  APPLICATION  OF  RADIO  TO 

EVERYDAY  BUSINESS 


IF  radio  has  a  legitimate  place  in  the  home  in  the  way 
of  amusement  and  education,  it  has  an  even  greater 
place  in  everyday  business,  especially  that  kind  of  busi- 
ness which  extends  out  beyond  the  narrow  confines  of 
our  immediate  city  and  State  and  country  and  even  con- 
tinent. Radio  is  a  logical  method  of  long-distance  com- 
mAmication.  It  is  alone  in  the  ship-to-ship  communication 
field,  and  it  takes  its  place  beside  the  telegraph  and  cable 
systems  in  our  present  scheme  of  things. 

Little  need  be  said  about  the  marine  end  of  radio. 
Suffice  it  to  remind  ourselves  that  virtually  every  ship 
that  carries  passengers  and  any  freighter  of  consequence 
are  equipped  with  radio.  No  greater  factor  was  ever  in- 
troduced in  maritime  circles  than  radio,  for  ships  are  no 
longer  out  of  touch  with  the  world  for  days  at  a  time. 
With  the  highly  efficient  ship  installations  as  well  as  the 
powerful  land  stations,  a  ship  is  rarely  isolated. 

Radio  World-Wide  Chains  in  the  Making 

W^hile  radio  may  be  used  for  short  distances  in  place 
of  telegraph  lines,  its  real  forte  lies  rather  in  long-distance 
work,  side  by  side  with  the  usual  cables.  It  has  been 
employed  for  inter-city  work  with  some  degree  of  suc- 
cess ;  but  if  all  inter-city  communication  were  conducted 


260 


RADIO  FOR  EVERYBODY 


by  radio  instead  of  by  the  usual  telegraph  system  it  is 
obvious  that  the  problem  of  interference  would  assume 
gigantic  and  finally  prohibitive  proportions. 

All   the  leading  nations   have   fully  realized  the  value 


Germany's  scheme  of  1913  for  world  communication.  A  study 
of  this  networli  indicates  that  it  is  clearly  influenced  to  a 
great  extent  by  military  as  well  as  commercial  considerations. 
The  World  War  caused  the  permanent  abandonment  of  this 
scheme. 

of  radio  as  a  means  of  long-distance  communication.  The 
recent  war  taught  all  nations  that  cables  and  telegraph 
lines  can  be  severed,  but  the  radio  system  cannot  be 
interrupted.  The  nation  with  powerful  radio  stations  is 
always  assured  of  communication  with  the  outside  world. 
A  number  of  world  schemes  of  radio  communication 
have  been  proposed  in  the  past,  and  some  of  them  are 
in  the  process  of  present  realization.  The  earliest  one 
is  shown  in  the  accompanying  map.  For  this  and  the 
other  maps  shown  in  the  following  pages,  as  well  as  for 
much  of  the  data  on  this  phase  of  radio,  the  author  is 
indebted  to  Alfred  N.  Goldsmith,  Director,  Research  De- 
partment, Radio  Corporation  of  America,  and  to  the 
Journal  of  the  American  Institute  of  Electrical  Engin- 
eers, in  which  Mr.  Goldsmith's  data  appeared.  The  ac- 
companying map,  in  which  the  distances  are  given  in 
kilometers  (a  kilometer  is  roughly  3/5  of  a  mile)  repre- 


RADIO  FOR  EVERYBODY 


v^Gl 


sents  the  extremely  ambitious  German  scheme  of  1913 
and  is  clearly  influenced  to  a  great  extent  by  military  as 
well  as  commercial  considerations.  The  length  of  some 
of  the  jumps  from  station  to  station,  taking  into  consider- 
ation the  transmitting  powers  and  the  types  of  receiving 
apparatus  then  available,  indicate  that  only  partial  or  oc- 
casional service  over  the  longer  spans  could  have  been 
expected,  and  then  only  at  low  speeds.  It  also  appears 
that  each  station  was  to  handle  several  channels  and 
therefore  presumably  to  divide  its  time  between  it?  vari- 
ous correspondent  stations.  This  type  of  service  is  more 
suited  to  press  and  propaganda  work  and  light  traffic 
than  it  is  to  the  more  exacting  high-speed  commercial 
requirements.  This  plan  was  not  carried  far  before  the 
war  brought  about  its  complete  destruction. 

Our  next  map  represents  the  first  British  Imperial 
schemes  for  radio  communication,  the  so-called  *'A11-Red 
Chain.''  It  dates  from  1913,  and  was  the  plan  of  the 
British  ^larconi  Company  which  submitted  it  to  the 
British  Government  for  approval.  It  was  adopted,  and 
some  work  was  done  along  the  lines  indicated  when  the 
war   intervened.     The   changes    caused  by  the   war   and 


The  British  Imperial  communication  scheme  of  1913,  the  so- 
called  "All-Red  Chain."  This  scheme  was  adopted  and  some 
work  was  done  along  the  lines  indicated  when  the  war  inter- 
vened. The  distances  were  too  great,  how^ever,  and  the  scheme 
was  abandoned. 


2-62 


RADIO  FOR  EVERYBODY 


other  causes  led  to  its  discontinuance  and  to  rather  seri- 
ous differences  between  the  British  Government  and  the 
Marconi  Company.  Afterwards  the  claims  of  the  Marconi 
Company  were  in  part  allowed  and  suitable  financial  com- 


British  Imperial  scheme  of  1919  for  radio  communication. 
This  is  a  less  ambitious  but  more  practical  scheme  than  that 
of  1913.  London  is  connected  with  distant  points  by  means 
of  short  spans  and  relays,  so  that  the  distances  are  entirely 
feasible. 

pensation  paid  by  the  British  Government  for  the  loss  of 
the  original  contractual  profits.  The  plan  itself  included 
two  routes  from  England  to  Australia  with  only  two  re- 
lays. It  was  a  scheme  involving  large  spans.  London 
was  the  main  center  from  which  most  of  the  communica- 
tion to  distant  points  radiated  directly. 

In  1919  and  1920  a  British  Government  Committee  re- 
considered the  entire  project  of  the  Imperial  radio  scheme 
and  recommended  the  less  ambitious  scheme  shown  in  our 
next  map.  Here  the  Western  Hemisphere  is  apparently 
neglected.  London  is  not  connected  directly  (without 
relays)  to  the  more  distant  points,  the  average  span  is 
shorter,  and  the  terminal  points  chosen  are  indicated  ap- 
parently only  in  part  by  commercial  considerations.  This 
system  will  be  Government-owned  and  operated,  which 
may  account  for  the  nature  of  this  plan,  which  is  now 
being  carried  out.  Only  a  very  small  portion  of  this 
plan  has  been  carried  out  thus  far. 


RADIO  FOR  EVERYBODY 


263 


Another  very  ambitious  plan  is  due  to  France  and  is 
given  in  the  accompanying  map.  It,  too,  is  not  planned 
entirely  along  commercial  lines.  Furthermore,  it  is  clear 
that  the  French  stations  are  intended  to  divide  their  time 
between  a  number  of  terminal  stations  and  that  ex- 
tremely long  spans  are  planned.  Of  the  stations  shown 
on  the  French  plan,  several  are  built  and  several  more 
are  in  process  of  construction.  A  considerable  portion 
of  this  plan  will,  however,  still  have  to  be  worked  out  in 
the  future.  It  is  noticeable  that  both  the  present  French 
plan  and  the  original  German  plan  lay  more  stress  on 
South  American  traffic  than  does  the  present  British  Im- 
perial scheme. 

Our  Scheme  for  World-Wide  Radio 
Then  we  come  to  our  own  pet  scheme  for  world-wide 
radio — America's  plan.  It  differs  in  several  important 
respects  from  the  preceding-  plans.  In  the  first  place, 
every  station  shown  thereon  is  either  in  operation  or  under 
construction,  and  'by  far  the  greater  portion  of  the  stations 
are  those  already  in  operation.  Furthermore,  for  the  sake 
of  clearness,  the  large  contemplated  expansions  of  this 
plan  are  not  shown  on  the  map,  although  they  will  add 


~— ^^N 

^          t      •           ^ 

^M^ 

>.$ 

■^  f    *> 

H /^o     y> 

^^^  r^ 

jr-y^r     '  Si^ 

^     V           Scandma^  (L, 

f^    ' 

f^             ■^prrfL''P^- Central  Europe 

^/k 

I        Unrted  ^^£: 

ii--:s^=^^^^^Z-—-:^^^^^?t^  I 

^\% 

PJ 

^-^"^^Y^^^ 

^W--.     -   ■ 

Central  AmwSr2^T. 
and  Antilles     ^W^ 

-.    y\Lo\\ 

^SS^ 

^/       BrazzavillA 

V) 

C)" 

yC           south  Af}^ 

^v  /. 

'i 

/=...    ■ 

• 

The  French  communication  scheme.  The  French  stations  are 
evidently  intended  to  divide  their  time  between  a  number  of 
terminal  stations  and  the  spans  are  extremely  long.  How- 
ever, work  is  progressing  on  several  large  stations  for  this 
world-wide   scheme. 


264 


RADIO  FOR  EVERYBODY 


nearly  as  many  more  channels  of  communication  to  the 
system  as  those  already  shown.  In  the  second  place,  the 
plan  shown  is  preeminently  a  commercial  one,  both  in  the 
placing  of  the  terminal  stations  and  in  the  practically 
exclusive  use  of  each  American  station  for  a  single 
channel.  This  latter  feature  permits  the  speedy  handling 
of  large  volumes  of  traffic  and  avoids  the  troul)lesome 
delays  which  result  when  the  time  of  a  transmitting  sta- 
tion is  excessively  "chopped  up"  or  divided  between  too 
many  receiving  stations.  The  system  is  one  of  moderate 
and  long  spans,  this  being  dictated  to  some  extent  by  the 


Our    American    scheme    for    world-wide    radio    communication. 

Every    station    sliown    in    this    map    is    either    in    operation    or 

under    construction,    and    by    far    the    greater    portion    of    the 

stations  are  those  already  in   operation. 

geographical  location  of  the  United  States,  its  particular 
communication,  needs,  and  the  absence  of  American  po- 
sessions  at  certain  points.  The  needs  of  the  United  States, 
considering  these  circumstances,  have  very  greatly  stim.u- 
lated  to  the  technical  improvement  of  radio  communication, 
and  have  led  to  the  satisfactory  solutions  of  the  problems 
of  long-distance  communication.  The  case  is  an  inter- 
esting illustration  of  the  stimulating  and  helpful  influence 
of  natural  obstacles. 

It  has  long  been  known  that  traffic  from  one  country  to 
another   is  by    no   means   evenly   distributed   throughout 


266  RADIO  FOR  EVERYBODY 

the  twenty-four  hours  of  the  day,  the  days  of  the  week,  or 
the  months  of  the  year.  There  are  very  pronounced  peaks, 
and  depressions  or  lull  of  traffic  found  to  exist.  Thus, 
the  traffic  between  two  countries  will  generally  be  heaviest 
for  the  hours  during  which  daylight  is  common  to  both, 
and  will  drop  to  a  minimum  during  the  week  end.  It 
would  be  desirable  to  handle  the  peak  of  the  load  without 
permitting  traffic  to  pile  up,  but  this  may  not  always  be 
feasible  for  reasons  of  economy,  both  of  equipment  and 
of  necessary  personnel.  This  has  led  to  the  attempt  to 
secure  a  high  load  factor  for  communication  circuits  by 
encouraging  some  of  the  users  of  the  service  to  accept  a 
certain  delay  in  the  delivery  of  their  messages  which  are 
then  sent  at  a  reduced  rate.  Thus  we  find  in  addition  to 
normal  messages,  which  are  sent  irt  the  order  in  which 
they  are  received,  the  "deferred"  messages  which  are 
sent  at  the  earliest  opportunity  when  traffic  has  slackened 
sufficiently  to  permit  their  introduction.  "Night  letters" 
and  ''week  end  letters'*  are  sent  during  the  periods  in- 
dicated, and  are  obviously  intended  to  fill  an  otherwise  dull 
period  in  the  circuit.  On  some  circuits,  "urgent"  mes- 
sages are  accepted  which  take  priority  over  all  others,  and 
require  the  payment  of  a  considerably  increased  rate.  As 
a  general  rule,  the  minimum  number  of  classes  of  mes- 
sages required  to  maintain  an  acceptable  load  factor  is 
desirable  not  only  because  of  the  increased  routine  in 
handling  traffic  of  many  different  classes  but  also  because 
of  the  confusion  in  the  public  mind  and  the  possible  dis- 
satisfaction which  results  when  the  type  of  service  rendered 
in  any  given  case  is  not  clearly  understood  in  advance. 

The  huge  radio  stations  for  inter-continental  work  are 
interesting  studies.  One  of  these  stations  is  the  Radio 
Central,  located  at  Rocky  Point,  Long  Island,  some  70 
miles  east  of  New  York  City.  However,  the  actual  opera- 
tion of  this  station  takes  place  from  New  York  City,  the 
dots  and  dashes  being  formed  by  an  operator  in  New 
York  City  and  sent  over  telegraph  lines  to  the  Radio 
Central  station,  where  they  are  automatically  transferred 


2'68  RADIO  FOR  EVERYBODY 

to  the  powerful  radio  transmitter,  consisting  of  a  num- 
ber of  200-kilowatt  high-frequency  generators.  Radio 
Central  is  in  realty  several  stations  in  one.  It  comprises 
a  number  of  separate  transmitters  so  as  to  ensure  simul- 
taneous communication  with  a  number  of  stations  abroad. 

Operating  a  Trans-Atlantic  Station  at  a  Distance 

It  has  always  been  a  problem  to  control  several  hun- 
dred kilowatts  of  power  at  frequencies  of  20,000  cycles  per 
second  by  breaking  it  up  into  the  dots  and  dashes  of  the 
telegraph  code  at  speeds  as  high  as  100  words  per  minute 
or  more.  When  it  is  considered  that  this  is  equivalent 
to  starting  and  stopping  the  flow  of  power  fifty  times 
per  second,  accurately  and  faultlessly,  and  that  the  initial 
control  power  is  merely  the  few  watts  that  can  be  drawn 
from  the  terminals  of  a  telegraph  line,  the  magnitude  of 
the  problem  becomes  evident.  By  the  development  of 
high-speed  power  relays  and  the  new  "'magnetic  amplifier," 
the  problem  has  been  very  elegantly  solved.  The  mag- 
netic amplifiers  at  the  Rocky  Point  station  enable  the 
powerful  transmitters  to  be  operated  at  long  distance,  so 
to  speak.  These  ferromagnetic  devices  accurately  modu- 
late or  control  the  flow  of  power  from  the  alternators  to 
the  radiating  system  or  aerial  wires. 

To  radiate  the  large  amounts  of  power  required  to 
bridge  transoceanic  stretches,  a  large  and  lofty  radiating 
system  or  aerial  is  required.  The  main  tower  at  Tucker- 
ton  (N.  J.)  is  850  feet  high.  At  the  New  Brunswick  (N. 
J.)  station  a  row  of  400-foot  masts  stretching  6,000  feet 
from  the  station  support  the  ''multiple  tuned"  aerial  sys- 
tem. The  latest  form  of  aerial  is  that  employed  at  the 
Radio  Central  station.  It  consists  of  a  line  of  410-foot 
towers  with  150-foot  spreaders  at  the  top  of  each,  and 
stretching  a  mile  and  a  half  from  the  station  building.. 
Twelve  such  rows  of  towers,  each  fed  by  its  own  high- 
frequency  alternators  and  constituting  in  effect  a  separate 
transmitting  station,  will  enable  the  Radio  Central  sta- 
tion to  be  used .  for  simultaneous  communication  with  an 


2:^a 


Twelve  of  the  seventy-two  steel  towers  comprising  the  aerial  supports 

of  the  Radio   Central  wireless   station.     Each  tower  is  410  feet  high, 

while  the  cross-arm  measures  150  feet  from  tip  to  tip. 


270  RADIO  FOR  EVERYBODY 

equal  number  of  receiving  stations  abroad  when  com- 
pletely realized.  An  area  of  about  ten  square  miles  is 
being  devoted  to  this  giant  station,  which  will  be  by  far 
the  largest  in  the  world  when  completed. 

In  radio  reception  there  have  also  been  very  marked 
advances  during  the  last  few  years.  Each  row  of  appara- 
tus in  its  especially  shielded  cases  is  capable  of  handHng 
one  transoceanic  channel.  Each  operator  is  provided  with 
a  telegraph  key  controlling  the  transmitter  on  the  corre- 
sponding circuit,  so  that  he  can,  if  necessary,  "break" 
or  interrupt  the  transmitting  operator  to  obtain  a  correc- 
tion or  other  information  from  the  station  which  he  is 
receiving. 

When  reception  at  high  speed  was  desired,  recording 
was  sometimes  accomplished  on  modified  phonographs 
which  were  run  rapidly  and  the  records  were  later  trans- 
scribed  at  lower  speeds  by  a  number  of  operators.  This 
method  of  receiving  at  high  speed  has  been  superseded  by 
modern  forms  of  ink  recorders  especially  developed  for 
radio  reception.  Photographic  recorders,  in  which  the 
received  signals  are  photographed  as  a  wavy  line  on  a 
paper  ribbon,  have  also  been  used  in  high  speed  reception. 

Wire  and  radio  communication,  according  to  Mr.  Gold- 
smith, should  work  hand  in  hand  in  any  comprehensive 
scheme  of  world  communication.  The  land  wires  and 
cables  have  very  clearly  demonstrated  their  great  capabili- 
ties and  usefulness ;  but  radio  communication,  even  at  this 
early  state  in  its  development,  has  shown  that  it  should 
be  considered  as  an  integral  element  of  any  well-considered 
plan  for  communicating  all  over  the  globe.  Today  ap- 
proximately 15  per  cent  of  the  traffic  across  the  Atlantic 
from  the  United  States  is  handled  via  radio,  which  is  a 
hopeful  showing  for  a  new  art,  to  be  sure.  To  the  extent 
that  there  is  harmonious  and  intelligent  co-operation  be- 
tween the  various  communication  systems,  we  may  hope 
for  the  satisfactory  solution  of  the  problem  of  giving  every 
person  on  earth  rapid  and  reliable  communication. 


Looking  up  at  the  top  of  one  of  the  steel  towers  of  the  Kadio  Central 

wireless    station.      The    cross-arm    at    the    top    serves    to    support    the 

sixteen  wires  which  form  the  aerial. 


272  RADIO  FOR  EVERYBODY 

When  Wire  and  Wireless  Work  Together 

Fortunately,  there  are  no  physical  limitations  to  prevent 
the  interconnection  by  skilled  persons  of  wire  line  and 
radio  circuits.  Messages  received  by  radio  telegraphy  or 
radio  telephony  can  be  automatically  transferred  to  wire 
lines  and  over  them  relayed  to  any  point  reached  by  them. 
Conversely,  telegraph  or  telephone  .signals  on  a  wire  line 
can  be  used  to  control  radio  telegraph  or  radio  telephone 
transmitters.  So  that  any  wire  system  may  be  extended 
by  the  addition  of  radio  relays  and,  reciprocally,  any 
radio  system  may  be  extended  by  the  addition  of  wire 
relays.  This  process  of  adding  wire  and  radio  Hnks  or 
relays  to  each  other  can  be  carried  on  to  practically  any 
desired  extent  and  should  constitute  an  element  in  the 
communication  systems  of  the  future.  On  a  moderate 
scale  it  is  being  carried  out  commercially  today  in  the 
case  of  messages  from  European  countries  received  by 
the  Radio  Corporation  of  America  at  its  receiving  stations 
on  Long  Island  and  in  New  Jersey.  From  these  points 
the  messages  are  automatically  relayed  over  wire  lines 
to  the  New  York  traffic  office  of  the  company  in  the  heart 
of  the  financial  district,  where  the  receiving  operators 
take  down  the  messages  by  ear,  if  sent  at  hand  speed,  or 
the  messages  are  automatically  written  down  by  ink  re- 
corders if  received  at  high  speed. 

A  similar  transfer  of  telephone  signals  to  and  from 
wire  hues  has  been  demonstrated  as  a  commercial  propo 
sition  in  highly  successful  fashion  by  the  American  Tele- 
phone &  Telegraph  Company,  in  the  Avalon-Los  Angeles 
radio  toll  circuit,  in  which  regular  radio  telephone  mes- 
sages are  sent  by  radio  over  a  31 3^  air  gap  without  the 
subscribers  realizing  that  their  conversation  is  being 
handled  in  any  other  manner  than  by  wires.  Experiments 
have  been  carried  on  with  the  steamship  Gloucester  and 
the  Deal  Beach  radio-phone  experimental  station,  and  per- 
sons have  talked  over  the  regular  telephone  instrument 
in  their  home  to  the  ship  at  sea.  More  recently,  still 
more  spectacular  experiments  have  been  carried  on  with 


liooking   up   through   the    center   of   one   of   the    steel   towers.      While 

this    steel    work    may    appear    delicate    because    of    its    simplicity,    it 

possesses   great   strength  because  of  the   diagonal   bracing. 


274  RADIO  FOR  EVERYBODY 

the  steamship  ''America''  while  400  miles  out  at  sea. 
It  is  only  a  matter  of  time  when  we  shall  be  able  to 
'phone  to  the  ship  at  sea  with  the  same  ease  that  we 
call  up  long-distance  points. 

Certain  countries,  such  as  the  United  States,  are  so 
situated  geographically  as  to  serve  naturally  as  important 
relay  centers  for  inter-continental  communications.  Com- 
munications from  Europe  to  South  America,  and  from 
Europe  to  the  Far  East  naturally  pass  over  the  United 
States.  In  view  of  the  rapid  rate  at  which  the  power, 
required  to  bridge  a  certain  distance  reliably  by  radio, 
increases  with  distance  for  spans  of  more  than  a  few 
thousand  miles,  it  is  advantageous,  holds  Mr.  Goldsmith, 
to  establish  relay  points  in  the  United  States  whereby 
communications  from  Europe  to  the  regions  named  will 
be  received  in  the  United  States  and  thence  automatically 
or  otherwise  relayed  to  their  destinations. 

The  Traffic  Capacity  of  the  Long-Distance  Ether 

Some  doubt  may  have  been  entertained  by  engineers  as 
to  the  traffic-carrying  capacity  of  the  ether  for  long-dis- 
tance communication.  The  figures  for  long-distance  tele- 
graphy can  be  at  least  roughly  estimated  without  serious 
difficulty.  We  shall  assume  continuous  wave  transmis- 
sion, with  an  appropriate  form  of  key  modulation  in 
sending  the  dots  and  dashes,  and  without  any  tone  modula- 
tion whatever.  Under  these  conditions,  and  taking  into 
account  both  side  bands  produced  as  the  result  of  actual 
transmission,  it  has  been  found  that  a  speed  of  100  words 
(or  500  letters)  per  minute  corresponds  to  the  occupa- 
tion of  a  band  of  frequencies  in  the  ether  roughly  100 
cycles  wide.  This  is  on  the  basis  that  the  radio-fre- 
quency generator  maintains  its  frequency  constant  during 
transmission.  We  shall  also  assume  that  the  receiver  is 
sufficiently  selective  to  exclude  all  signals  on  frequencies 
outside  of  this  100  cycle  band.  Under  these  conditions, 
we  may  say  roughly  that  on  each  cycle  per  second  of 
available   ether   frequencies   we   can   transmit   one   word 


The  power  plant  and  station  building  of  the  Radio  Central  wireless 
station.  In  the  foreground  are  the  sprays  and  cooling  basin  for 
cooling   and   condensing    purposes,   forming   part   of   the   power   plant 

operation. 


276  RADIO  FOR  EVERYBODY 

per  minute.  Assuming  further  that  long-distance  traffic 
will  be  handled  in  the  range  of  wave  lengths  between 
6,000  meters  and  40,000  meters,  a  reasonable  assump- 
tion on  the  basis  of  present-day  practice — and  also  a 
conservative  one — we  shall  have  available  a  band  of  ether 
frequencies  of  from  50,000  to  7,500  cycles  per  second, 
or  42,500  cycles  in  all.  According,  we  can  ultimately 
transmit  at  least  42,500  words  per  minute  via  radio  over 
long  distances,  or  no  less  than  61,200,000  words  per  day. 
If  we  extend  the  range  of  available  wave  lengths  for  long- 
distance communication  below  6,000  meters  through  the 
further  reduction  of  atmospheric  disturbances ;  if  we 
eliminate  one  of  the  side  bands  resulting  from  transmis- 
sion; and  if  we  assume  the  possibility  of  using  the  same 
wave  length  for  transmission  at  several  points  of  the 
earth's  surface  with  directional  discrimination  between 
several  transmitters  at  the  receiving  station,  the  already 
enormous  daily  message-carrying  capacity  of  the  ether 
will  be  greatly  increased.  As  a  matter  of  comparison, 
we  may  state  that  the  figure  of  61,200,000  words  per 
day  is  roughly  150  times  the  actual  traffic  sent  across  the 
Atlantic  Ocean  by  cable  and  radio  at  the  present  time. 

A  number  of  perfectly  reasonable  requirements  must  be 
met  by  transmitting  and  receiving  stations  in  order  to 
realize  the  ultimate  capacity  mentioned  above,  according 
to  Mr.  Goldsmith.  The  transmitters  must  have  strictly 
constant  generator  frequency  consistent  with  their  key 
signaling  speed  and  the  receivers  must  be  highly  selective 
for  a  correspondingly  narrow  range  of  frequencies  and 
yet  follow  the  signals  accurately.  Even  today  radio  en- 
gineers are  confident  that  these  results  will  shortly  be 
obtained  by  carefully  chosen  technical  expedients. 

The  nature  of  world  communication  makes  it  interna- 
tional in  character.  Both  wire  lines  and  radio  waves  know 
nothing  of  national  boundaries,  a  fact  which  is  sometimes 
resented  by  the  nations,  particularly  during  hostilities. 
It  is  this  essentially  international  character  of  long-dis- 
tance    communications,     particularly     of     the     unguided 


278  RADIO  FOR  EVERYBODY 

variety,  which  has  led  to  the  international  regulation  of 
radio  communication.  In  1912,  the  London  Radio  Con- 
vention was  agreed  to  by  most  of  the  nations  of  the 
world  and  given  force  by  corresponding  national  legisla- 
tion in  each  case.  These  regulations  of  the  London  Con- 
vention were  fairly  general  in  character  and  covered  the 
most  essential  points  only.  Thus  there  was  left  con- 
siderable and  proper  leeway  for  each  nation  to  settle  its 
own  national  problems  in  communication  according  to 
local  needs  and  the  nature  of  local  institutions.  It  would 
seem  that  some  such  policy  is  wise,  especially  where  im- 
portant matters  of  truly  international  scope  clearly  require 
settlement  in  the  interests  of  eiTecive  communication  and 
to  avoid  inevitable  disputes.  Beyond  this  point  which  is 
defined  without  much  difficulty  by  the  experts  in  the  art, 
regulation  becomes  burdensome  and  tends  to  retard  the 
progress  of  the  radio  art  and  to  discourage  initiative. 

For  the  rapid  growth  of  world  communication,  as  far 
as  a  radio  is  concerned  the  degree  of  regulation  of  the  art 
by  the  various  governments  should  be  restricted  to  the 
enforcement  of  the  international  regulations  together 
with  such  control  of  the  nationality  of  the  owners  and 
personnel  of  the  radio  companies  as  may  be  deemed  nec- 
essary for  national  security.  The  entire  field  of  un- 
guided  communication,  as  Mr.  Goldsmith  calls  radio,  is 
so  new  and  is  developing  so  rapidly  that  great  harm  can 
be  done  by  well-meaning  but  injudicious  legislators  and 
officials.  Like  all  pioneer  arts,  its  successful  and  speedy, 
development  depends  on  wide  freedom  of  experiment  by 
enterprising  investigators  and  encouragement  of  effort  on 
the  part  of  wide-awake  companies. 


Chapter  XL 

HOW  TO  CONSTRUCT  SIMPLE  RADIO 
RECEIVING  SETS  FOR  RADIO- 
PHONE PROGRAMS 


AND  now  for  those  who  wish  to  construct  their  own 
simple  receiving  outfits,  here  is  a  chapter  devoted 
to  their  particular  interests. 

First  of  all  we  shall  describe  an  entire  receiving  station, 
including  antenna  as  well  as  a  crystal  detector  receiving 
set.  This  station  will  enable  one  to  hear  the  messages  sent 
from  medium^ower  transmitting  stations  within  an  area 
about  the  size  of  a  large  city,  and  to  hear  high-power 
stations  within  50  miles,  provided  the  waves  used  by  those 
stations  have  wave  frequencies  between  500  and  1500 
kilocycles  per  second,  which,  translated  into  plain  Ens^lish, 
means  w^ave  lengths  between  600  and  200  meters.  Much 
greater  distances  are  often  covered,  especially  at  night. 
If  a  person  constructs  the  coil  and  other  parts  as  indicated, 
the  total  cost  of  this  set  can  be  kept  down  to  about  $6.00. 
If,  however,  a  specially  efficient  outfit  is  desired,  the  cost 
may  be  about  $15.00. 

The  Essential  Parts  of  Receiving  Station 

The  set  about  to  be  described  has  been  designed  by  the 
Bureau  cf  Standards  at  the  request  of  the  States  Relations 
Service  of  the  United  States  Department  of  Agriculture, 
for  the  use  of  boys  and  girls  radio  clubs. 

There  are  five  essential  parts  to  this  receiving  station. 


280  RADIO  FOR  EVERYBODY 

as  well  as  any  other  receiving  station,  namely :  the  antenna, 
lightning  switch,  ground  connections,  receiving  set  proper, 
and  telephone  receivers.  The  received  signals  come  into 
the  receiving  set  through  the  antenna  and  ground  connec- 
tion. In  the  receiving  set  they  are  converted  into  an 
electric  current  which  produces  the  sounds  in  the  telephone 
receivers.  The  telephone  receiver  is  either  one  or  a  pair 
of  telephone  receivers  worn  on  the  head  of  the  listener. 
A  number  of  telephones  may  be  used  with  such  a  set, 
but  a  loud-speaking  device,  which  does  away  with  head 
phones,  is  not  practical  with  a  simple  set  of  this  kind. 

The  purpose  of  the  lightning  switch  is  to  protect  the 
receiving  set  from  damage  by  lightning.  It  is  used  to 
connect  the  antenna  directly  to  ground  when  the  receiving 
station  is  not  being  used.  When  the  antenna  and  the 
connection  to  the  ground  are  properly  made  and  the  light- 
ning switch  is  closed,  an  antenna  acts  as  a  lightning  rod 
and  is  a  protection  rather  than  a  source  of  danger  to  the 
building. 

The  principal  part  of  the  station  is  the  receiving  set 
proper.  In  the  set  described  in  the  following  paragraphs 
it  is  subdivided  into  two  parts,  the  tuner  and  the  detector, 
and  in  more  complicated  sets  still  other  elements  are  added. 

The  Antenna,  Lightning  Switch  and  Ground 
Connections 

The  antenna  is  simply  a  wire  suspended  between  two 
elevated  points.  Wherever  there  are  two  buildings,  or  a 
house  and  a  tree,  or  two  trees  with  one  of  them  very  close 
to  the  house,  it  relieves  one  of  the  need  of  erecting  one  or 
both  antenna  supports.  The  antenna  should  not  be  less 
than  30  feet  above  the  ground  and  its  length  should  be 
about  75  feet.  (See  Fig.  1.)  While  this  figure  indicates 
a  horizontal  antenna,  it  is  not  important  that  it  be  strictly 
horizontal.  It  is  in  fact  desirable  to  have  the  far  end  as 
high  as  possible.  The  "lead-in"  wire  or  drop-wire  from 
the  antenna  itself  should  run  as  directly  as  possible  to  the 
Hghtning  switch.  If  the  position  of  the  adjoining  build- 
ings or  trees  is  such  that  the  distance  between  them  is 


RADIO  FOR  EVERYBODY 


281 


greater  than  about  85  feet,  the  antenna  can  still  be  held 
to  a  75  foot  distance  between  the  insulators  by  increasing 
the  length  of  the  piece  of  rope  (D)  to  which  the  far  end 
of  the  antenna  is  attached.  The  rope  (H)  tieing  the 
antenna  insulator  to  the  house  should  not  be  lengthened 
to  overcome  this  difficulty,  because  by  so  doing  the  antenna 
"lead-in"  or  drop  wire  (J)  would  be  lengthened. 

Details  of  Parts — The  parts  will  be  mentioned  here  by 
reference  to  the  letters  appearing  in  Figures  1  and  2. 


Fig.  1. — Construction  of  antenna  for  reception  purposes.  A — 
screw  eye;  B — rope;  C — pulley;  D — rope;  E — insulator;  F — 
antenna;  G — Insulator;  H — rope;  I — screw  eye;  J — lead-in  wire; 
K — lightning:  switch;  L — ground  wire;  M — ground  pipe;  N — 
lead  to   receiving   set;    O^ — insulating   tube. 

A  and  I  are  screw  eyes  sufficiently  strong  to  anchor  the 
antenna  at  the  ends. 

B  and  H  are  pieces  of  rope  }i  or  j/z  inch  in  diameter, 
just  long  enough  to  allow  the  antenna  to  swing  clear  of 
the  two  supports. 

D  is  a  piece  of  ^  or  ^  inch  rope  sufficiently  long  to 
make  the  distance  between  E  and  G  about  75  feet. 

C  is  a  single  block  pulley  which  may  be  used  if  readily 
available. 


282  RADIO  FOR  EVERYBODY 

E  and  G  are  two  insulators  which  may  be  constructed 
of  any  dry  hardwood  of  sufficient  strength  to  withstand 
the  strain  of  the  antenna  ;  blocks  about  1^  x  2  x  10  inches 
will  serve.  The  holes  should  be  drilled  as  shown  in  Fig.  1 
sufficiently  far  from  the  ends  to  give  proper  strength.  If 
wood  is  used  the  insulators  should  be  boiled  in  paraffin 
for  about  one  hour.  If  porcelain  wiring  cleats  are  avail- 
able they  may  be  substituted  instead  of  the  wood  insulators. 
If  any  unglazed  porcelain  is  used  as  insulators,  it  should 
be  boiled  in  paraffin  the  same  as  the  wood.  Regular 
antenna  insulators  are  advertised  on  the  market,  but  the 
two  improvised  types  just  mentioned  will  be  satisfactory 
for  an  amateur  receiving  antenna. 

F  is  the  antenna  about  75  feet  between  the  insulators 
E  and  G.  The  wire  may  be  No.  14  or  16  copper  wire 
either  bare  or  insulated.  The  end  of  the  antenna  farthest 
from  the  receiving  set  may  be  secured  to  the  insulator 
(E)  by  any  satisfactory  method,  being  careful  not  to  kink 
the  wire.  Draw  the  other  end  of  the  antenna  wire  through 
the  other  insulator  (G)  to  a  point  where  the  two  insulators 
are  separated  by  about  75  feet,  twist  the  insulator  (G) 
so  as  to  form  an  anchor  as  shown  in  Fig.  1.  The  re- 
mainder of  the  antenna  wire  (J)  which  now  constitutes 
the  ''lead-in"  or  drop-wire  should  be  just  long  enough 
to  reach  the  lightning  switch. 

K  is  the  lightning  switch.  For  the  purpose  of  a  small 
antenna  this  switch  may  be  the  ordinary  porcelain  base, 
30  ampere,  single-pole  double-throw  battery  switch.  These 
switches  as  ordinarily  available  have  a  porcelain  base  about 
1  by  4  inches.  The  "lead-in"  wire  (J)  is  attached  to  this 
switch  at  the  middle  point.  The  switch  blade  should 
always  be  thrown  to  the  lower  clip  when  the  receiving 
set  is  not  actually  being  used  and  to  the  upper  clip  when 
it  is  desired  to  receive  signals. 

L  is  the  ground  wire  for  the  lightning  switch;  it  may 
be  a  piece  of  the  same  size  wire  as  used  in  the  antenna, 
of  sufficient  length  to  reach  from  the  lower  clip  of  the 
lightning  switch  (K)  to  the  clamp  on  the  ground  rod  f  M). 

M  is  a  piece  of  iron  pipe  or  rod  driven  3  to  6  feet  into 


RADIO  FOR  EVERYBODY  283 

the  ground,  preferably  where  the  ground  is  moist,  and 
extending  a  sufficient  distance  above  the  ground  in  order 
that  the  ground  clamp  may  be  fastened  to  it.  Scrape  the 
rust  or  paint  from  the  pipe  before  driving  in  the  ground. 


Fig:.  2. — Arrangement   of  receiving-  instrument   and  connections 
with     antenna     and     ground..     J — lead-in     wire;     K — lightning 
switch;    Jj — ground    wire;    N — lead    to    receiving    set;    O — insu- 
lating tube;   P — receiving   set;    Q — ground  for  receiving   set. 

N  is  a  wire  leading  from  the  upper  clip  of  the  lightning 
switch  through  the  porcelain  tube  (O)  to  the  receiving 
set  binding  post  marked  "antenna." 

O  is  a  porcelain  tube  of  sufficient  length  to  reach 
through  the  window  casing  or  wall.  This  tube  should  be 
mounted  in   the  casing  or  wall   so   that  it   slopes   down 


284  RADIO  FOR  EVERYBODY 

toward  the  outside  of  the  building.  This  is  done  to  keep 
the  rain  from  following  the  tube  through  the  wall  to  the 
interior. 

Fig.  2  shows  the  radio  receiving  set  installed  in  some 
part  of  the  house. 

P  is  the  receiving  set  which  is  described  in  detail  below. 

N  is  the  wire  leading  from  the  ''antenna"  binding  post 
of  the  receiving  set  through  the  porcelain  tube  to  the 
upper  clip  of  the  lightning  switch.  This  wire,  as  well  as 
the  wire  shown  by  Q,  should  be  insulated  and  preferably 
flexible.  A  piece  of  ordinary  lamp  cord  might  be  un- 
braided  and  serve  for  these  two  leads. 

Q  is  a  piece  of  flexible  wire  leading  from  the  receiving 
set  binding  post  marked  "ground"  to  a  water  pipe,  heating 
system  or  some  other  metallic  conductor  to  ground,  except 
M,  Fig.  1.  If  there  are  no  water  pipes  nor  radiators  in 
the  room  in  w^hich  the  receiving  set  is  located,  the  wire 
should  be  run  out  of  doors  and  connected  to  a  special 
"ground"  below  the  window,  which  shall  not  be  the  same 
as  the  "ground"  for  the  lightning  switch.  It  is  essential 
that  for  the  best  operation  of  the  receiving  set  this 
"ground"  be  of  the  very  best  type.  If  the  soil  near  the 
house  is  dry  it  is  necessary  to  drive  one  or  more  pipes  or 
rods  sufficiently  deep  to  encounter  moist  earth  and  connect 
the  ground  wire  to  the  pipes  or  rods.  This  distance  will 
ordinarily  not  exceed  6  feet.  Where  clay  soil  is  encoun- 
tered this  distance  may  be  reduced  to  3  feet,  while  in 
sandy  soil  it  may  be  increased  to  10  feet.  If  some  other 
metallic  conductor,  such  as  the  casing  of  a  drilled  well,  is 
not  far  "away  from  the  window,  it  will  be  a  satisfactory 
"ground." 

TuNER^  Detector  and  Telephone 

At  least  the  telephone  will  have  to  be  purchased.  The 
tuner  and  certain  accessories  can  be  made  at  home. 

Tuner  {R,  Fig.  3) — This  is  a  piece  of  cardboard  or 
other  non-metallic  tubing  with  turns  of  copper  wire  wound 
around  it.  The  cardboard  tubing  may  be  an  oatmeal  box. 
Its  construction  is  described  in  detail  below. 


RADIO  FOR  EVERYBODY  285 

Crystal  Detector  (S,  Fig.  3) — The  construction  of  a 
crystal  detector  may  be  of  very  simple  design  and  quite 
satisfactory.  The  crystal,  as  it  is  ordinarily  purchased, 
may  be  unmounted  or  mounted  in  a  little  block  of  metal. 
For  mechanical  reasons  the  mounted  type  may  be  more 
satisfactory,  but  that  is  of  no  great  consequence.  It  is 
very  important,  however,  that  a  very  good  tested  crystal 
be  used.  It  is  probable  also  that  a  galena  crystal  will  be 
more  satisfactory  to  the  beginner. 

The  crystal  detector  may  be  made  up  of  a  tested  crystal, 
three  wood  screws,  short  pieces  of  copper  wire,  a  nail, 
set  screw  type  of  binding  post,  and  a  wood  knob  or  cork. 
The  tested  crystal  is  held  in  position  on  the  wood  base 
by  three  brass  wood-screws  as  shown  at  I  Fig.  3.  A  bare 
copper  wire  may  be  wrapped  tightly  around  the  three 
brass  screws  for  contact.  The  assembling  of  the  rest  of 
the  crystal  detector  is  quite  clearly  shown  in  Fig.  3. 

Plione  (T,  Fig.  3) — It  is  desirable  to  use  a  pair  of 
telephone  receivers  connected  by  a  head  band,  usually 
called  a  double  telephone  headset.  The  telephone  receivers 
may  be  any  of  the  standard  commercial  makes  having  a 
resistance  of  between  2000  and  3000  ohms.  The  double 
telephone  receivers  will  cost  more  than  all  the  other  parts 
of  the  station  combined  but  it  is  desirable  to  get  them, 
especially  if  one  plans  to  improve  his  receiving  set  later. 
If  one  does  not  care  to  invest  in  a  set  of  double  telephone 
receivers  a  single  telephone  receiver  with  a  head  band  may 
be  used;  it  gives  results  somewhat  less  satisfactory. 

Accessories — Under  the  heading  of  accessory  equip- 
ment may  be  listed  binding  posts,  switch  arms,  switch  con- 
tacts, test-buzzer,  dry  battery  and  boards  on  which  to 
mount  the  complete  apparatus.  The  binding  posts,  switch 
arms  and  switch  contacts  may  all  be  purchased  from 
dealers  who  handle  such  goods  or  they  may  be  quite  readily 
improvised  at  home.  There  is  nothing  peculiar  about  the 
pieces  of  wood  on  which  the  equipment  is  mounted.  They 
may  be  obtained  from  a  dry  packing-box  and  covered  with 
paraffin  to  keep  out  moisture. 


286  RADIO  FOR  EVERYBODY 

Details  of  Construction 

The  following  is  a  detailed  description  of  the  method 
of  winding  the  coil,  construction  of  the  wood  panels,  and 
mounting  and  wiring  the  apparatus. 

Tuner — See  R.  Fig.  3.  Having  supplied  one's  self  with 
a  piece  of  cardboard  tubing  4  inches  in  diameter  and 
about  y2  pound  of  No.  24  (or  No.  26)  double  cotton  cov- 
ered copper  wire,  one  is  ready  to  start  the  winding  of  the 
tuner.  Punch  two  holes  in  the  tybe  about  }^  inch  from 
one  end  as  shown  at  2  on  Fig.  3.  Weave  the  wire  through 
these  holes  in  such  a  way  that  the  end  of  the  wire  will  be 
quite  firmly  anchored,  leaving  about  12  inches  of  the  wire 
free  for  connections.  Start  with  the  remainder  of  the 
wire  to  wrap  the  several  turns  in  a  single  layer  about  the 
tube,  tightly  and  closely  together.  After  ten  complete 
turns  have  been  wound  on  the  tube  hold  those  turns  snugly 
while  a  tap  is  being  taken  ofif.  This  tap  is  made  by  making 
a  6  inch  loop  of  the  wire  and  twisting  it  together  at  such 
a  place  that  it  will  be  slightly  staggered  from  the  first  tap. 
This  method  of  taking  off  taps  is  shown  quite  clearly  at 
U,  Fig.  3.  Proceed  in  this  manner  until  six  twisted  taps 
have  been  taken  off  at  every  ten  turns.  After  these  first 
seventy  turns  have  been  wound  on  the  tube  then  take  off 
a  6  inch  twisted  tap  for  every  succeeding  single  turn  until 
ten  additional  turns  have  been  wound  on  the  tube.  After 
winding  the  last  turn  of  wire  anchor  the  end  by  weaving 
it  through  two  holes  punched  in  the  tube  much  as  was 
done  at  the  start,  leaving  about  12  inches  of  wire  free  for 
connecting.  It  is  to  be  understood  that  each  of  the  eighteen 
taps  is  slightly  staggered  from  the  one  just  above,  so  that 
the  several  taps  will  not  be  bunched  along  one  line  on  the 
cardboard  tube.  See  Fig.  3.  It  would  be  advisable,  after 
winding  the  tuner  as  just  described,  to  dip  the  tuner  in  hot 
parafiin.     This  will  help  to  exclude  moisture. 

Upright  Panel  and  Base — Having  completed  the  tuner 
to  this  point,  set  it  aside  and  construct  the  upright  panel 
shown  in  Fig.  4.  This  panel  may  be  a  piece  of  wood 
approximately  ^^  inch  thick.     The  position  of  the  several 


GROUND 


TUNLR. 


I-TURNTOEACHTAP 


I0-TURN5 
TO  EACH  TAP 


TWI5TE:DTAP 


^ 


i<?9Ai 


telephone:  receivers 


Fig.    3. — Constructional    details    of    the    simple    radio    receiving 

set  designed  by  the  U.   S.  Bureau  of  Standards  for  the  use  of 

laymen. 


288  RADIO  FOR  EVERYBODY 

holes  for  the  'binding  posts,  switch  arms  and  switch  con- 
tacts may  first  be  laid  out  and  drilled.  The  "antenna" 
and  "ground"  binding  posts  may  be  ordinary  Ys  inch  brass 
bolts  of  sufficient  length  and  supplied  with  three  nuts  and 
two  washers.  The  first  nut  binds  the  bolt  to  the  panel,  the 
second  nut  holds  one  of  the  short  pieces  of  stiff  wire, 
while  the  third  nut  holds  the  antenna  or  ground  wire  as 
the  case  may  be.  The  switch  arm  with  knob  shown  at  V, 
Fig.  3,  may  be  purchased  in  the  assembled  form  or  it  may 
be  constructed  from  a  thin  slice  cut  from  a  broom  handle 
and  a  bolt  of  sufficient  length  equipped  with  four  nuts 
and  two  washers  together  with  a  narrow  strip  of  thin 
brass  somewhat  as  shown.  The  switch  contacts  (W, 
Fig.  3)  may  be  of  the  regular  type  furnished  for  this 
purpose  or  they  may  be  brass  bolts  equipped  with  one  nut 
and  one  washer  each  or  they  may  even  be  nails  driven 
through  the  panel  with  an  individual  tap  fastened  under 
the  head  or  soldered  to  the  projection  of  the  nail  through 
the  panel.  The  switch  contacts  should  be  just  close  enough 
that  the  switch  arm  will  not  drop  between  the  contacts  but 
also  far  enough  apart  that  the  switch  arm  can  be  set  so 
as  to  touch  only  one  contact  at  a  time. 

The  telephone  binding  post  should  preferably  be  of  the 
set  screw  type  as  shown  as  X,  Fig.  3. 

Instructions  for  Wiring 

Having  constructed  the  several  parts  just  mentioned 
and  mounted  them  on  the  wood  base,  one  is  ready  to  con- 
nect the  several  taps  to  the  switch  contacts  and  attach  the 
other  necessary  wires.  Scrape  the  cotton  insulation  from 
the  loop  ends  of  the  sixteen  twisted  taps  as  well  as  from 
the  ends  of  the  two  single  wire  taps  coming  from  the 
first  and  last  turns.  Fasten  the  bare  ends  of  these  wires 
to  the  proper  switch  contacts  as  shown  by  the  correspond- 
ing numbers  in  Fig.  3.  One  should  be  careful  not  to  cut 
or  break  any  of  the  looped  taps.  It  would  be  preferable 
to  fasten  the  connecting  wires  to  the  switch  contacts  by 
binding  them  between  the  washer  and  the  nut  as  shown  at 
3,  Fig.  3.     A  wire  is  run  from  the  back  of  the  binding 


RADIO  FOR  EVERYBODY 


289 


post  marked  "ground"  (Fig.  3)  to  the  back  of  the  left- 
hand  switch-arm  bolt  (Y),  thence  to  underneath  the  left- 
hand  binding  post  marked  "phones."  A  wire  is  then  run 
from  underneath  the  right-hand  binding  post  market 
"phones"  to  underneath  the  binding  post  (4,  Fig.  3),  which 
forms  a  part  of  the  crystal  detector.  A  piece  of  No.  34- 
bare  copper  wire  about  2^  inc'hes  long,  one  end  of  which 
is  twisted  tightly  around  the  nail  (the  nail  passing  through 


Assembled    receiving    set,    ready    for    use.      This    little    set    ^vill 
receive   over   distances   of   25   to   possibly   35   miles   from   radio- 
phone  broadcasting    stations. 


binding  post  4)  the  other  end  of  which  rests  gently  by  its 
own  weight  on  the  crystal  (1).  The  bare  copper  wire 
which  was  wrapped  tightly  around  the  three  brPFs  wood- 
screws  holding  the  crystal  in  place  is  led  to  and  fastened 
at  the  rear  of  the  right-hand  switch-arm  bolt  (V),  thence 
to  the  upper  left-hand  binding  post  marked  "antenna." 
As  much  as  possible  of  this  wiring  is  shown  in  Fig.  3. 


290  RADIO  FOR  EVERYBODY 

Directions  for  Operating 

After  all  the  parts  of  this  crystal-detector  radio  receiv- 
ing set  have  been  constructed  and  assembled  the  first 
essential  operation  is  to  adjust  the  little  piece  of  wire, 
which  rests  lightly  on  the  crystal,  to  a  sensitive  point. 
This  may  be  accomplished  in  several  different  ways ;  the 
use  of  a  miniature  buzzer  transmitter  is  very  satisfactory. 
Assuming  that  the  most  sensitive  point  on  the  crystal  has 
been  found  by  method  described  in  paragraph  below,  "The 
Test  Buzzer,"  the  rest  of  the  operation  is  to  get  the  radio 
receiving  set  in  resonance  or  in  tune  with  the  station  from 
which  one  wishes  to  hear  messages.  The  tuning  of  the 
receiving  set  is  attained  by  adjusting  the  inductance  of  the 
tuner.  That  is,  one  or  both  of  the  switch  arms  are  rotated 
until  the  proper  number  of  turns  of  wire  of  the  tuner  are 
made  a  part  of  the  metallic  circuit  between  the  antenna 
and  ground,  so  that  together  with  the  capacity  of  the 
antenna  the  receiving  circuit  is  in  resonance  with  the  par- 
ticular transmitting  station.  It  will  be  remembered  that 
there  are  ten  turns  of  wire  between  each  of  the  first  eight 
switch  contacts  and  only  one  turn  of  wire  between  each 
two  of  the  other  contacts.  The  tuning  of  the  receiving  set 
is  best  accomplished  by  setting  the  right-hand  switch  arm 
on  contact  (1)  and  rotating  the  left-hand  switch  arm  over 
all  its  contacts.  If  the  desired  signals  are  not  heard,  move 
the  right-hand  switch  arm  to  contact  (2)  and  again  rotate 
the  left-hand  switch  arm  throughout  its  range.  Proceed 
in  this  manner  until  the  desired  signals  are  head. 

It  will  be  advantageous  for  the  one  using  this  radio 
receiving  equipment  to  find  out  the  wave  frequencies 
(wave  length)  used  by  the  several  radio  transmitting  sta- 
tions in  his  immediate  vicinity. 

The  Test  Buzzer — (Z,  Fig.  3) — ^As  mentioned  previ- 
ously, it  is  easy  to  find  the  more  sensitive  spots  on  the 
crystal  by  using  a  test  buzzer.  The  test  buzzer  is  used  as 
a  miniature  local  transmitting  set.  When  connected  to 
the  receiving  set  as  shown  at  Z,  Fig.  3,  the  current  pro- 
duced by  the  buzzer  will  be  converted  into  sound  by  the 


RADIO  FOR  EVERYBODY  291 

telephone  receivers  and  the  crystal,  the  loudness  of  the 
sound  depending  on  what  part  of  the  crystal  is  in  contact 
with  the  fine  wire.  To  find  the  most  sensitive  spot  connect 
the  test  buzzer  to  the  receiving  set  as  directed,  close  the 
switch  (5,  Fig.  3)  (and  if  necessary  adjust  the  buzzer 
armature  so  that  a  clear  note  is  emitted  by  the  buzzer),  set 
the  right-hand  switch  arm  on  contact  point  No.  8,  fasten 
the  telephone  receivers  to  the  binding  posts  marked 
"phones,"  loose  the  set  screw  of  the  binding  post  slightly 
and  change  the  position  of  the  fine  wire  (6,  Fig.  3)  to 
several  positions  of  contact  with  the  crystal  until  the 
loudest  sound  is  heard  in  the  phones,  then  tighten  the 
binding  post  set  screw  (4)  slightly. 

Approximate  Cost  of  Parts 

The  following  list  shows  the  approximate  cost  of  the 
parts  used  in  the  construction  of  this  radio  receiving 
station.  The  total  cost  will  depend  largely  on  the  kind 
of  apparatus  purchased  and  on  the  number  of  parts  con- 
structed at  home. 
Antenna — 

Wire — ^^Copper,  bare  or  insulated.  No.  14, 
100  to  150  feet,  about 0.75 

Rope — 3/^  or  ^  inch 2  cents  per  foot 

2  insulators,  porcelain 0.20 

1  pulley 0.15 

Lightning  switch — 30  ampere  battery  switch.    0.30 

1  porcelain  tube 0.10 

Ground  Connections — 

Wire  (same  kind  as  antenna  wire). 

1  clamp 0.15 

1  iron  pipe  or  rod 0.25 

Receiving  Set — 

Yz  pound  No.  24  copper  wire  double  cot- 
ton covered 0.75 

1 ' cardboard  box. 

2  switch  knobs  and  blades  complete 1.00 

18  switch  contacts  and  nuts 0.75 

3  bindings  posts — set  screw  type 0.45 


292  RADIO  FOR  EVERYBODY 

2  binding  posts — any  type 0.30 

1  crystal— tested 0.25 

3  wood  screws,  brass,  ^  inch  long 0.03 

Wood  for  panels  (from  packing  box). 

2  pounds  paraffin 0.30 

Lamp  cord 2  to  3  cents  per  foot 

Test  buzzer 0.50 

Dry  battery 0.30 

Telephone  receivers 4.00  to  8.00* 


Total  11.00    15.00 

*Still  more  efficient  and  expensive  telephone  receivers 
are  available  at  prices  ranging  to  about  $20.00. 

If  nothing  but  the  antenna  wire,  lightning  switch,  por- 
celain tube,  crystal,  telephone  receiver,  bolts  and  buzzer 
are  purchased  this  total  can  be  reduced  to  about  $6.00. 

A  Simple  Vacuum  Receiving  Set 

Using  the  same  antenna,  ground  connection  and  light- 
ning switch  as  already  described,  the  more  ambitious  radio 
enthusiast  may  readily  construct  a  simple  vacuum  tube 
receiving  set  which  will  give  better  results  than  the  crystal 
detector  set  although  it  is  considerably  more  complicated. 

This  set,  which  is  shown  completely  assembled  in  the 
accompanying  drawing,  comprises  a  loose-coupler  tuner, 
provided  with  primary  and  secondary  switches,  primary 
and  secondary  variable  condenser,  grid  leak,  vacuum  tube, 
vacuum  tube  socket,  filament  rheostat,  filament  battery 
and  high  voltage  or  plate  battery.  If  necessary,  most  of 
the  material  may  be  home  made,  with  the  exception  of 
the  vacuum  tube,  grid  leak,  vacuum  tube  socket,  batteries, 
filament  rheostat  and  telephone  receivers. 

The  first  step  is  to  construct  the  loose-coupler  tuner. 
This  consists  of  a  primary  and  a  secondary  winding,  each 
one  being  tapped  off  at  every  ten  turns  and  the  taps  being 
brought  to  the  switch  points  of  the  primary  and  secondary 
switches.  The  primary  is  a  mailing  tube  measuring  five 
or  six  inches  in  diameter,  on  which  is  wound  100  turns 
of  No.  20,  22  or  24  B.  &  S.  gauge  double  cotton  or  double 


s 

11 


o 
c  2 


f  3 


0. 

i         ^ 

2          s 

7771                  O                          - 

u  / 

^                                        2 

2 

6 

?-?       J 

O 

;? 

\                                         -1 

z 

0 

z 

H 

1 

\xj?-^^ 

a^s 

^^   ^^ 

i/w-' 

H 
n 

1 

;^^^^^ 

$$^    ; 

V 

i^^^^^W^ 

/y  \r_ 

/ 

1 

C^    y 

/M  A 

MWa^ 

^^^^/  /// 

^-^^w^-^L       / 

1/^ 

u(  // 

li 

'\r 

\|i    1 

^^~l     5 

IJl 

J        F 

\\|    1 

^    1— i              ^     i 

\\\| 

^^^    i    ■<            .     ^      ^ 

\iu\ 

^^^^SS           ■vk                                                                            03 

\>\\\ 

^^^^S-      ^                               o        ni 

vl 

^^       1                                 c 

\  m\\ 

^^^^^^r;          /ol            l/l            ■                     JO 

\m\\     /I 

^^^^^=^^       ^i        rn                       2 

\  \\\    m 

i    ^^^^^^=^^                '7i                ^                                               0* 

11 

il^ft^    1 

§  vl' 

l\  ^B  1    < 

>    \  W 

i\\  \    ^^s=^    ^                                        — 1 

^    \i\\ 

^     \\\\ 

l\/^S  1  /^        ^^^^^ 

V 

AW^^g^  ^           ^^^^^^ 

Ar- 

li.''* 

^^^^^ 

PI     \ 

ITH- 

/|i 

-s^^-  i'.';^-   ~^  ---    ~-^^^:::= 

i/    &^ 

H 

Vl/  ^ 

/' 

!  K^                  o 

\  \  \V  V        "0 

1 

i                 2                      Z 

\    A  ^■'y                  0 

1  ^ 

1                 0                      H 

\  A  /              H 

i            z                (yi 

LV              a 

0                t 
1             "0                 -^ 

-^-  ■-=■ 

0                   O 

1               H 

f 

J 

294  RADIO  FOR  EVERYBODY 

silk  covered  wire,  with  the  adjacent  turns  side  by  side. 
At  every  ten  turns  the  wire  is  looped  and  twisted  together 
so  as  to  form  a  tap,  the  loop  being  passed  through  a  hole 
in  the  mailing  tube  and  the  tap  brought  over  to  its  respec- 
tive switch  point,  to  which  it  is  connected  after  the  primary 
is  ready  for  assembling.  The  final  turn  of  the  primary 
is  passed  through  two  holes  close  together  so  as  to  hold 
the  winding  firmly  in  place,  and  the  end  brought  to  the 
last  switch  point.  When  the  primary  is  completely  wound, 
it  is  mounted  on  a  block  of  wood  which  acts  as  the  sup- 
port. It  is  left  largely  to  the  builder  as  to  how  the  primary 
is  mounted.  One  method  is  to  use  a  round  piece  of  wood 
of  about  the  same  diameter  as  the  inside  measurement 
of  the  mailing  tube.  This  block  is  nailed  on  the  end  piece 
and  the  mailing  tube  is  slipped  over  the  block  to  which  it 
can  be  firmly  glued  or  tacked.  The  taps  have,  of  course, 
been  scraped  and  connected  with  their  respective  switch 
points. 

Now  for  the  secondary.  This  is  constructed  in  virtually 
the  same  manner,  using  a  smaller  mailing  tube  which  fits 
inside  the  primary  tube.  The  winding  is  of  the  same  sized 
wire  for  the  sake  of  simplicity,  and  taps  are  taken  at  every 
ten  points  and  brought  to  their  respective  points  of  a  ten- 
point  switch.  The  mounting  of  the  secondary  must  be 
carried  out  in  the  same  manner  as  the  primary,  except 
that  the  latter  has  a  stationary  support,  nailed  firmly  on 
the  base  board  of  the  loose-coupler,  while  the  former  has 
a  movable  support.  The  movalDle  support  is  made  up  in 
the  manner  indicated  in  our  drawing,  so  that  the  secondary 
can  be  moved  in  and  out  of  the  primary,  between  guides. 

This  completes  the  loose-coupler.  The  next  step  is  to 
construct  variable  condensers,  which  are  necessary  for 
fine  tuning.  Inasmuch  as  the  loose-coupler  tunes  only  in 
big  steps  of  ten  turns  at  a  time,  it  is  necessary  to  employ 
variable  condensers  in  order  to  effect  sharp  tuning  so 
essential  in  the  satisfactory  reception  of  radio-pnone 
service. 

The  simplest  variable  condenser  to  construct  is  probably 
the  so-called  book  type,  which  is  illustrated  in  our  drawing. 


RADIO  FOR  EVERYBODY 


295 


This  consists  of  two  pieces  of  wood,  which  are  fastened 
together  by  means  of  an  ordinary  hinge,  so  that  they  may 
be  moved  toward  each  other  or  drawn  apart,  as  the  case 
may  be.  A  small  wooden  strip  or  even  a  nail  prevents  the 
two  pieces  from  coming  into  actual  contact.  On  each 
strip  of  wood  is  mounted  a  piece  of  sheet  aluminum  or 
copper,  which  acts  as  one  of  the  condenser  plates.  Bind- 
ing posts  are  used  in  the  manner  indicated  to  make  proper 

BINDING     POST 


COPPER    OR 
ALUMINUM     PLATES 


BUMPER 


HINGE 


Top    view    of    book   type    of   variable    condenser,    consisting:    of 

two  boards  hinged  together,  two  pieces  of  copper  or  aluminum 

sheeting,   arranged  as    shown. 

connections.  The  capacity  of  such  a  condenser  is  in- 
creased by  moving  the  plates  close  together  and  lessened 
by  moving  them  farther  apart. 

Items  That  Must  Be  Bought 

The  grid  leak  consists  of  a  very  high  resistance  unit. 
This  is  obtained  by  drawing  a  pencil  line  on  a  sheet  of 
paper,  and  clamping  this  pencil  line  between  two  heavy 
copper  washers  so  that  the  grid  current  for  the  vacuum 
tube  must  flow  through  this  exceedingly  high  resistance. 
However,  the  grid  leak  has  to  be  constructed  with  con- 


296  RADIO  FOR  EVERYBODY 

siderable  accuracy,  so  that  it  may  be  the  part  of  better 
judgment  to  purchase  a  grid  leak  at  any  radio  supply 
store.  It  is  a  matter  of  50  or  75  cents,  and  it  is  certain  to 
be  correctly  designed  and  constructed. 

The  vacuum  tube  must  be  purchased,  of  course,  and 
aside  from  the  telephone  receivers  and  batteries,  it  repre- 
sents the  most  expensive  single  item  for  such  a  set.  The 
tube  must  be  a  detector  tube,  also  known  as  a  gassy  tube, 
and  costs  either  $4.00  or  $5.00,  depending  on  the  type 
employed.  A  vacuum  tube  socket  must  also  be  purchased, 
at  a  cost  of  anywhere  from  50  cents  to  $1.50,  depending 
on  the  type  selected. 

A  vacuum  tube  requires  two  batteries,  namely,  the 
filament  battery  of  six  volts  and  the  B  or  plate  battery 
of  22^  volts.  A  6-volt  storage  battery  gives  the  best 
service  for  filament  current,  because  the  heavy  drain  of 
the  vacuum  tube  filament  soon  wears  out  any  dry  battery. 
Still,  if  the  reader  is  going  to  construct  his  own  set  it  is 
almost  certain  that  he  will  not  want  to  go  to  the  expense 
of  purchasing  a  storage  battery,  hence  dry  batteries  must 
be  used.  Four  or  five  cells  of  dry  battery  may  be  used, 
although  it  will  increase  the  life  of  the  dry  cells  a  great 
deal  if  two  sets  are  employed,  connected  in  what  is  known 
as  series-parallel.  That  is  to  say,  four  or  five  cells  are 
connected  in  series,  with  the  carbon  of  one  coil  going  to 
the  zinc  of  the  next  cell.  Then,  the  zinc  of  one  battery  is 
connected  with  the  zinc  of  the  other  battery,  and  the 
carbon  of  one  battery  with  the  carbon  of  the  other  battery. 
This  arrangement  gives  a  battery  of  twice  the  amperage 
or  current,  and  the  drain  caused  by  the  tube  is  not  so 
serious. 

The  filament  rheostat  may  be  made,  although  it  will 
hardly  pay  when  simple  rheostats  can  be  purchased  for 
one  dollar  or  less.  The  rheostat  serves  to  control  the 
filament  current,  which  must  be  accurately  regulated  for 
satisfactory  results,  since  the  vacuum  tube  is  a  delicate 
piece  of  mechanism. 

The  B  or  plate  battery  must  be  purchased.    This  battery 


RADIO  FOR  EVERYBODY 


297 


comes  in  a  compact  block,  either  in  the  large  or  the  small 
size.  There  are  two  types  of  B  battery,  namely,  the  fixed 
voltage  and  the  variable  voltage  types.  The  latter  is  rec- 
ommended, since  it  permits  of  regulating  the  plate  voltage 
applied  to  the  vacuum  tube,  and  this  is  a  most  important 
consideration  with  many  vacuum  tubes. 

The  telephone  receivers  must  be  bought,  and  it  is  well 
to  invest  in  good  receivers.  If  there  is  anything  that 
tends  to  make  or  undo  a  radio  receiving  set  it  is  the  tele- 
phone receivers.  Inexpensive  receivers  are  certain  to 
prove  the  most  expensive  in  the  long  run,  because  the 


Arrangement    of    dry    cells    in    series-parallel,    in    order    to 

obtain   a    steadier    voltage    and   a   longer   life   from    the    dry 

battery  used  with  vacuum  tubes. 


owner  of  such  receivers  may  soon  tire  of  them  and  ask 
for  something  better,  only  to  find  that  his  inexpensive 
receivers  have  no  market  value  and  must  therefore  be 
junked. 

With  all  the  various  components  constructed  and  pur- 
chased, ready  for  use,  they  are  assembled  as  shown  in  our 
assembly  drawing.  To  operate  the  set,  the  primary  switch 
is  placed  on  the  middle  switch  point  and  the  variable  con- 
denser in  the  aerial-ground  or  primary  circuit  is  varied 
slowly.  ^leanwhile,  the  secondary  switch  is  also  placed 
on  the  middle  switch  point,  and  the  secondary  condenser 
is  also  varied.     When  the  desired  signal  or  radio-phone 


298  RADIO  FOR  EVERYBODY 

service  is  intercepted,  the  switches  and  variable  condensers 
are  rapidly  adjusted  until  the  best  results  are  obtained. 
All  the  while,  of  course,  the  vacuum  tube  is  lighted  and 
the  filament  rheostat  is  carefully  adjusted  for  the  loudest 
yet  clearest  sounds. 

Such  a  set  will  work  satisfactorily  over  a  range  of  50 
miles,  although  it  is  not  as  satisfactory  as  one  using  the 
Armstrong  regenerative  or  feed-back  circuit,  which  is 
somewhat  more  involved  and  is  described  further  on  in 
simple  form  for  home  construction  purposes.  However. 
the  various  radio  supply  houses  are  now  offering  the 
various  components  for  regenerative  receiving  sets,  as  well 
as  amplifier  units.  An  excellent  receiving  set  may  be 
constructed  by  purchasing  a  vario-coupler,  two  vario- 
meters, grid  leak  and  grid  condenser,  and  the  various 
other  accessories  such  as  the  rheostat,  vacuum  tube  and 
socket,  binding  -posts,  and  so  on,  connected  as  shown  in 
our  chapter  on  receiving  sets. 

For  really  good  results,  as  far  as  a  home-made  set 
is  concerned,  it  is  necessary  to  employ  the  regenerative 
arrangement.  This  arrangement,  as  has  already  been 
described  elsewhere  in  this  work,  is  virtually  a  self-am- 
plifier, and  adds  a  great  deal  to  the  efficiency  of  the  re- 
ceiving set. 

One  of  the  very  best  yet  simple  receiving  arrangements 
which  has  come  to  the  attention  of  the  author  and  which 
he  has  constructed  for  his  own  experimental  use,  is  shown 
in  the  accompanying  drawings.  It  is  a  verv  simple  form 
of  two-circuit  receiving  set,  using  a  plate  variometer 
for  the  feed-back  or  regenerative  agent. 

First  of  all,  it  is  necessary  to  construct  the  main  tuning 
member,  which  is  simply  a  mailing  tube  measuring  3^ 
inches  in  diameter  by  4  inches  long,  on  which  two  wind- 
ings are  carefully  wound.  The  first  winding  consists  of 
twenty  turns  of  No.  20  B.  &  S.  gauge  double  cotton  cov- 
ered wire,  wound  close  together,  of  course,  while  the  sec- 
ond winding,  starting  one-eighth  away  from  the  end  of 
the  first  winding,  consists  of  40  turns  of  same  sized  wire, 
also  wound  close  together.    The  windings  should  be  held 


I 

5  ^ 


0«! 


9 

or;  & 


s  o 


1  o 


p  p 
o  & 
X  p 
-3 

ii 

9 


300  RADIO  FOR  EVERYBODY 

in  place  simply  by  making  holes  in  the  cardboard  tube 
and  passing  the  ends  of  the  windings  through  these  holes. 
Under  no  circumstances  should  the  windings  be  varnished 


-40  TURNS 


FIBRE    SHELL 


How  the  fixed  winding:  of  the  variometer 
is  made.  A  frame  work  is  built  up  with 
sheet  fiber  on  a  square  form,  and  held 
together  Avith  shellac  or  glue.  The  wind- 
ing   is    placed     on    this    form,    as     shown. 

or  shellacked,  as  this  introduces  certain  undesirable  char- 
acteristics. Both  windings  are  fixed,  their  wave  length 
values  being  altered  by  variable  condensers  as  shown  in 
the  accompanying  wiring  diagram. 

The  variable  condensers  may  be  of  the  home-made 
variety,  using  the  book  type  already  referred  to  in  the 
previous  set.  Two  such  condensers  will  be  necessary, 
and  it  is  well  to  make  them  of  good  size  so  that  they 
will  have  ample  capacity.  One  condenser  is  placed  across 
the  primary  winding — or  in  series  with  it  if  the  wave 
length  of  the  antenna-ground  circuit  is  to  be  reduced — 
while  the  other  is  placed  across  the  secondary  winding. 


RADIO  FOR  EVERYBODY 


301 


A  fixed  condenser  must  be  constructed.  This  consists 
of  nothing  more  formidable  than  a  number  of  sheets  of 
tin  foil  separated  by  pieces  of  paraffined  paper.  A  good 
condenser  may  be  made  by  cutting  ten  pieces  of  tin  foil 
so  that  they  will  measure  one  inch  wide  by  three  inches 
long  and  cutting  eleven  pieces  of  paraffined  paper  so  that 
they  measure  one  and  one-quarter  inches  wide  by  two 
and  one-half  inches  long.  The  paraffined  paper  and  the 
tin  foil  sheets  are  assembled  in  staggered  order  as  shown 
in  the  accompanying  sketch.  The  pile  of  tin-foil  and 
paraffined  paper  can  be  placed  between  two  pieces  of 
cardboard  and  held  together  by  means  of  a  rubber  band 
or  piece  of  thread  wrapped  around  the  cardboard  end 
pieces. 

The  grid  leak  had  best  be  purchased,  for  it  is  a  rather 


40  TURNS 


FIBRE  SHELL 


Completed  variometer,  showing  the  movable  coil  partly  turned. 
The   fixed  and  the  movable  windings   are   connected  in    series, 
so    that    the    current    must    pass    through    both    of    them,    one 
after  the  other. 


302  RADIO  FOR  EVERYBODY 

difficult  thing  to  make  even  though  it  does  not  consist  of 
more  than  a  pencil  line  drawn  on  a  piece  of  good  paper 
and  clamped  between  two  copper  washers.  If  the  con- 
structor wishes  to  build  the  grid  leak  as  well  as  other 
parts  of  the  set,  he  is  welcomed  to  try  it,  although  it 
would  seem  that  since  this  item  costs  but  50  cents  to  buy 
it  ready  made — and  properly  made — it  is  best  not  to 
waste  time  and  effort  in  trying  to  construct  a  grid  leak. 

Then  we  come  to  the  filament  rheostat.  Here  again,  it 
is  best  to  purchase  a  manufactured  filament  rheostat, 
which  may  run  all  the  way  from  75  cents  to  $2.00,  depend- 
ing on  how  well  it  is  made.  The  tube  socket  must 
also  be  purchased,  representing  an  outlay  of  from  75  cents 
to  $2.00,  depending  on  the  type  selected. 

The  "A"  battery  is  the  filament  battery,  and  consists 
of  either  a  dry  battery,  preferably  composed  of  ten  dry 
cells  arranged  in  series  multiple  as  depicted  on  page  297, 
or  a  6-volt  20-ampere-hour  storage  battery.  The  "B" 
battery  is  the  high-voltage  battery  for  the  plate  circuit. 
It  consists  of  a  single  block  of  battery  supplying  22>^- 
volt  current.  The  telephone  receivers  may  be  a  single 
receiver  or  a  regular  head-set,  according  to  taste — and 
pocktbook.  Finally,  there  is  the  variometer  used  as  the 
feed-back  device. 

The  variometer  had  best  be  purchased,  for  it  is  a  difficult 
instrument  for  the  home  constructor  to  tackle.  Of  course, 
a  variometer  may  be  constructed,  because  it  consists 
simply  of  a  fixed  winding  and  a  corresponding  turnable 
winding.  But  the  point  in  the  case  is  to  make  a  variom- 
eter that  will  work  properly,  and  that  requires  a  little  ex- 
perience and  skill. 

However,  if  the  builder  insists  on  constructing  the 
variometer,  he  may  do  so.  A  simple  design  is  shown  in 
the  accompanying  sketch.  It  consists  of  a  stationary 
wooden  frame,  built  up  in  the  manner  indicated,  and  a 
movable  frame.  Now  the  stationary  winding  is  placed  on 
a  form  made  of  fiber  strip,  shellacked  together  to  make 
it  strong.  This  frame,  with  its  winding,  is  placed  inside 
the  stationary  frame.    The  movable  winding,  on  the  other 


TINFOIL 


TINFOJL 


PAPER 
SEPARATORS 


THREAD     FASTENINGS 


11^^^ 


TERMINAL     WIRE 


How  the  fixed  coupler  is  made,  and  the  construction 
of  the  small  fixed  condenser.  The  first  drawing 
shows  the  mailing  tube  with  twenty  turns  and  forty 
turns  for  the  primary  and  secondary  windings.  The 
second  drawing  shows  the  assembly"  of  the  fixed  con- 
denser. The  third  shows  a  side  view  of  the  assembled 
condenser. 


304 


RADIO  FOR  EVERYBODY 


hand,  is  wound  on  the  movable  form,  as  indicated.  Each 
winding  should  consist  of  60  turns  of  No.  20  double 
cotton  covered  wire.  No  nails  should  be  used  in  making 
this  instrument,  glue  or  wooden  pegs  being  used  through- 
out. A  suitable  shaft  should  be  provided,  so  that  the 
movable  coil  can  be  turned  by  means  of  a  handle.  A  dial 
can  be  drawn,  with  graduations  from  1  to  100,  or  a  dial 


±A 


I'I'MI'I 


How  the  various  components  of  the  simple  regenerative  set 
are  connected  together.  A — antenna;  G — ground;  P — primary; 
S — secondary;  VCl — primary  condenser;  VC2 — secondary  con- 
denser; FC — fixed  condenser;  GL, — grid  leak;  VT — detector 
tube;  A — filament  battery;  B — "B"  or  plate  battery;  K — rheo- 
stat;  T — telephone  receivers;   V — variometer  for  feed-back. 


and  handle  can  be  purchased  from  any  radio  supply  house. 
However,  after  all  is  said  and  done,  the  best  results  will 
be  obtained  by  purchasing  a  variometer,  since  this  is  a 
rather  difficult  instrument  to  construct — and  construct 
right. 

The  set  is  arranged  as  shown  in  our  assembly  drawing. 
It  is  a  simple  set  to  operate  and  permits  of  extremely 
sharp  tuning.     The  regenerative  arrangement  makes  for 


^•3 


So 

'to 


f  O  ^1 

C  ;:  or; 
(R  X  « 

a  C  n 

p  5"  5' 

"a! 
«  p  » 


j;  3  ffi 


306  RADIO  FOR  EVERYBODY 

excellent  results,  so  that  this  set  will  receive  from  radio- 
phone broadcasting-  stations  over  100  miles  away  under 
favorable  circumstances,  without  an  amplifier.  With  an 
amplifier,  which  may  be  readily  constructed  by  purchasing 
the  necessary  components  and  assembling  them  in  the 
manner  indicated  by  the  wiring  diagrams  in  the  chapter 
dealing  with  amplifiers,  the  range  may  be  materially  in- 
creased. 

Some  companies  are  now  offering  complete  receiving 
sets  in  knockdown  form,  so  that  the  purchaser  can  wind 
the  coils  and  assemble  the  components  himself,  thus  sav- 
ing considerable  money  and  gaining  practical  knowledge 
in  radio  construction.  These  sets  are  highly  recommended 
to  those  who  desire  to  build  their  own  apparatus  yet  wish 
the  best  type  equipment  now  available. 


Chapter  XII. 


THE  RADIO  TELEPHONE  OF  TODAY 
AND  TOMORROW 


ASIDE  from  the  broadcasting  o£  interesting  pro^ 
grams,  the  radio  telephone  has  other  and  very  im- 
portant uses.  It  must  become  a  part  of  the  regular  wire 
telephone  system;  indeed,  it  already  forms  part  of  our 
telephone  system,  although  only  in  an  experimental  way. 

The  Radio  Link 

There  is  genuine  romance  in  the  story  of  the  radio 
telephone.  A  dozen  years  ago  it  was  a  crude  laboratory 
toy,  with  little  prospect  of  ever  becoming  a  practical,  work- 
aday thing.  It  was  handicapped  with  a  most  unsavory 
reputation,  because  it  had  been  made  the  catspaw  of 
fraudulent  stock-selling  enterprises.  The  very  publicity 
which  had  been  accorded  in  unstinted  measure  had  done 
untold  harm,  for  the  general  public  had  come  to  expect 
too  much  of  this  young  and  quite  unwieldy  means  of 
rcommunication. 

The  radio  telephone  started  out  as  a  competitor  of  the 
wire  telephone,  although  in  truth  it  could  never  hope  to 
rival  the  more  conventional  system.  Yet  the  radio  tele- 
phone only  started  on  its  practical  career  when  the  tele- 
phone engineers — the  very  men  against  whom  this  newer 
form  of  communication  was  to  compete — took  an  interest 
in  certain  radio  equipment,  particularly  vacuum  tubes,  and 


308 


RADIO  FOR  EVERYBODY 


General  scheme  of  the  radio  link  as   used  between  tlie  California  main 

phone    system    with    that    of    the    Santa    Catalina    Island    and    making 

arrangement,  so  that  two  messages  can  be 

developed  them  to  a  practical  point.  Today,  the  radio 
telephone  is  not  a  competitor  of  the  wire  telephone:  it 
is  an  accessory.  It  became  practical  through*  the  efforts 
of  the  telephone  engineers,  but  in  turn  it  has  made  wire 
telephony  possible  over  longer  distances  and  with  greater 
clearness  than  could  ever  have  been  possible  with  the 
former  equipment. 

The  radio  telephone  today  is  part  and  parcel  of  our 
wire  telephone  system,  and  it  is  fast  becoming  as  practical 
as  the  latter.  Indeed,  were  it  not  for  the  high  cost  of  this 
form  of  communication,  it  would  be  quite  within  present 
accomplishments  for  any  telephone  subscriber  to  call  up  a 
relative  or  friend  on  an  ocean  liner  several  hundred  miles 
off  shore,  the  voice  being  carried  over  the  usual  telephone 
line  to  the  central  office,  through  trunk  lines  to  the  distant 
radio  transmitter,  and  thence  transmitted  through  the  air 
to  the  steamer.     The  radio  link,  as  the  radio  telephone 


RADIO  FOR  EVERYBODY  309 


land  and_  the  island  of  Santa  Catalina,  connecting  the  mainland  tele- 
them  a  single  system.  The  radio  link  in  this  installation  is  a  duplex 
handled  at  one  time,  or  one  in  each  direction. 

service  is  called  when  made  a  part  of  the  usual  wire  tele- 
phone system,  is  destined  to  become  commonplace  within 
the  next  few  years. 

Now  the  foregoing  is  not  a  mere  flight  of  fancy.  It 
is  a  matter  of  record  that  the  American  Telephone  & 
Telegraph  Company  recently  conducted  a  series  of  experi- 
ments with  radio  links  and  the  transcontinental  telephone 
line.  Telephonic  communication  was  established  between 
the  steamship  "Gloucester,"  cruising  off  Deal  Beach,  N. 
J.,  and  Santa  Catalina  Island,  situated  some  thirty  miles 
off  the  California  coast  in  the  vicinity  of  Long  Beach. 
The  telephonic  communication,  in  this  case,  passed  from 
the  "Gloucester"  to  Deal  Beach,  N.  J. ;  from  Deal  Beach 
to  New  York  via  telephone  line ;  from  New  York  to 
San  Francisco  via  transcontinental  telephone  line;  from 
San  Francisco  to  Los  Angeles  via  telephone  line;  from 
Los  Angeles  to  Long  Beach  via  telephone  Hne ;  from  Long 


310 


RADIO  FOR  EVERYBODY 


Beach  by  radio  to  Pebbly  Beach,  on  Santa  Catalina 
Island.  From  ocean  to  ocean  via  radio,  telephone  line  and 
radio  again! 

The  first  commercial  radio  and  connecting  land  toll  line 
is  the  Santa  Catalina  Island  and  California  radio  link, 
which  was  set  in  operation  well  over  a  year  ago.  Radio 
telephone  service  between  Santa  Catalina  and  the  main- 
land to  connect  up  with  the  Bell  System  exchanges  was 
installed  at  the  request  of  the  local  telephone  company. 
Catalina  Island  is  one  of  the  great  tourist  resorts  in  Cali- 


€" 


» 


i&^,  ,,...^;.   :...  -'V;':"^-^"^' 

i 

SAMTA                                'V^ 

CATALINA  SS                        ',  ^ 

T~~-v        \                  ,/  '"^ 

~-    f-v     .; 

'              '•».    f/ 

A^  PEBBu 
^~  7<^'BeACH 

AVALON 

Map   and   diagrram   showing   the  radio   link   between  the   Cali- 
fornia mainland  and  Santa  Catalina  Island,  and  the  wire  sys- 
tems at  either  end,  all  of  which  function  as  a  single  unit  when 
connected   together   in   this   manner. 


fornia.  It  attracts  thousands  of  visitors  daily  throughout 
the  year,  who,  heretofore,  when  they  left  the  California 
mainland,  remained  completely  isolated  from  the  rest  of 
the  world  until  they  returned  to  Los  Angeles,  except  for 
a  much-overloaded  naval  radio  telegraph  station  on  the 
island. 

That  this  radio  link,  which  bridges  the  31^-mile  gap 


RADIO  FOR  EVERYBODY  311 

between  the  island  and  the  mainland,  is  not  in  the  experi- 
mental stage  may  be  gathered  from  the  fact  that  it  han- 
dles hundreds  of  messages  each  day.  The  large  amount 
of  commercial  traffic  with  scarcely  any  interruption  which 
the  Avalon-Los  Angeles  toll  circuit  has  carried  every  day 
since  its  opening,  is  an  ample  proof  of  the  practicability 
of  toll  lines  containing  radio  links,  where,  due  to  physical 
conditions,  direct  wire  connections  are  impracticable. 

Mechanism  of  the  Radio  Links 

It  is  virtually  impossible  to  delve  deeply  into  the  intri- 
cacies of  the  Avalon-Los  Angeles  radio  link  and  toll  cir- 
cuit, since  it  involves  the  most  elaborate  telephone  and 
radio  engineering  practice.  Suffice  it  to  say  that  the  dia- 
gram at  the  left  of  page  310  shows  schematically 
the  Avalon-Los  Angeles  circuit,  consisting  of  a  little  more 
than  one  mile  of  wire  line  from  the  Avalon  central  office 
to  Pebbly  Beach,  a  31^-mile  radio  link  to  Long  Beach, 
and  25  miles  additional  wire  circuit  to  Los  Angeles.  This 
combination  wire  and  radio  circuit  is  operated  as  a  unit 
providing  through  telephone  and  signalling  from  Avalon 
to  Los  Angeles.  At  Avalon  the  circuit  may  be  connected 
with  any  subscriber's  line  and  at  Los  Angeles  to  any  local 
subscriber's  line,  through  local  exchanges,  or  with  other 
long-distance  lines  reaching  practically  any  subscriber  in 
the  Bell   System. 

The  difficulties  overcome  to  surmount  interference  from 
radio  stations  along  the  Pacific  Coast  and  a  naval  station 
on  Catalina  Island,  together  with  the  many  sets  on  ships, 
were  many,  we  learn  from  the  engineers  of  the  American 
Telephone  &  Telegraph  Company  and  the  Western  Elec- 
tric Company,  who  installed  the  radio  link.  Practically 
uninterrupted  service  now  has  been  made  possible,  how- 
ever, and  the  quality  of  the  transmitted  speech  is  almost 
perfect;  so  much  so,  in  fact,  that  a  user  of  the  telephone 
service  that  includes  the  radio  link  notices  virtually  no 
difference  in  the  service. 

Among  some  of  the  technical  obstacles  it  was  found  nec- 
essary to  overcome  before  satisfactory  operation  of  the 


312  RADIO  FOR  EVERYBODY 

radio  link  was  possible  was  the  problem  of  housing  the 
receiver  and  transmitting  apparatus  in  the  same  building 
or  in  close  proximity.  This  was  accomplished  by  properly 
shielding  all  leads,  shielding  the  receiver  to  prevent  cross- 
talk from  the  transmitter,  and  the  use  of  specially  designed 
filter  circuits  for  the  receiver. 

The  radio  link  is,  in  truth,  a  link.  It  functions  as  part 
of  the  regular  telephone  system  with  little  or  no  extra 
complication,  so  far  as  the  everyday  operation  and  use  of 
the  system  is  concerned.  Operators  are  located  at  the  cen- 
tral offices  in  Los  Angeles  and  Avalon,  operating  ordinary 
telephone  switchboards.  They  handle  the  radio  link  traf- 
fic in  the  same  manner  as  if  the  wire  circuits  were  being- 
handled.  They  ring  up  in  the  same  way  by  the  operation 
of  the  usual  ringing  key.  In  fact,  the  installation  of  a 
voice  frequency  ringing  system,  which  permits  the  use  of 
a  ringing  key  at  the  regular  exchange  switchboards  in 
Los  Angeles  and  Avalon,  for  signalling  gave  rise  to  some 
trouble  and  necessitated  some  changes  in  design  before  it 
was  successfully  placed  in  operation.  This  was  due  to  the 
fact  that  the  apparatus  was  rushed  for  the  installation 
before  it  had  been  given  a  thorough  field  trial  by  the  engi- 
neering department  of  the  Western  Electric  Company. 

The  radio  link  is  a  duplex  system;  that  is  to  say,  one 
message  may  be  sent  in  each  direction  simultaneously. 
For  transmitting,  a  fair-sized  aerial  is  employed,  as  indi- 
cated in  bird's-eye  view  on  pages  308  and  309,  while  for  re- 
ceiving a  loop  antenna  is  used  at  each  end.  These  loops 
are  of  the  solenoidal  type,  six  feet  square,  and  consist  of 
only  four  or  five  turns  each.  To  make  the  duplex  opera- 
tion a  success,  it  goes  almost  without  saying  that  excep- 
tional measures  had  to  be  taken,  otherwise'  the  transmitter 
at  one  end  would  drown  out  the  incoming  signals  on  the 
loop  antenna  but  a  short  distance  away.  The  elimination 
of  such  interference  was  attained  by  the  use  of  different 
carrier  frequencies  for  transmission  in  the  two  directions. 
Filters,  amplifiers  and  repeaters  are  employed  in  large 
numbers,  the  basis  of  all  this  equipment  being  the  im- 
proved vacuum  tube.    An  interesting  feature  of  the  receiv- 


314  RADIO  FOR  EVERYBODY 

ing  apparatus  is  the  provision  of  relays  which  close  a 
buzzer  alarm  circuit  when  the  filament  of  any  vacuum 
tube  fails. 

The  radio  transmitter  employed  at  either  end  makes  use 
of  a  circuit  in  which  the  oscillations  are  generated  directly 
in  the  antenna  circuit.  The  modulation  of  the  radio  car- 
rier frequency  is  accomplished  by  what  is  known  as  the 
"constant  current  system,"  in  which  both  oscillator  and 
modulator  tubes  are  of  50  watts  rating.  These  tubes  are 
of  the  coated  filament  type,  having  relatively  low  filament 
power  consumption  and  very  constant  operating  charac- 
teristics. The  transferring  of  the  speech  current  from  the 
telephone  line  to  the  radio  link  is  an  elaborate  process. 
Briefly,  it  may  be  described  in  this  manner :  The  speech 
current  is  applied  to  a  speech  amplifier  tube,  through  an 
im/put  transformer.  The  output  of  this  amplifier  is  im- 
pressed on  the  grid  circuits  of  the  two  parallel  modulator 
tubes  through  a  transformer.  The  action  of  these  modu- 
lator tubes  is  that  of  an  amplifier  and  their  ouput  voltage 
is  impressed  on  the  plate  circuits  of  the  two  oscillator 
tubes  by  means  of  a  reactance,  which  is  common  to  the 
modulator  and  oscillator  plate  circuits.  This  modulation 
of  the  oscillator  plate  potential  results  in  speech  frequency 
variation  of  the  amplitude  of  the  antenna  current.  The 
frequency  of  the  antenna  current  when  not  modulated  is 
nearly  that  corresponding  to  the  free  period  of  the  antenna 
circuit. 

A  Record  to  be  Proud  Of 

Since  the  radio  link  is  the  only  telephone  channel  be- 
tween the  island  and  the  mainland,  it  was  very  heavily 
overloaded  from  the  day  of  opening  until  the  cessation  of 
the  summer  tourist  traffic  in  the  latter  part  of  September, 
1920.  Due  to  the  methods  employed,  the  high  grade  cir- 
cuit, and  so  on,  a  great  deal  more  traffic  is  handled  over 
this  circuit  than  is  generally  handled  by  a  single  toll  line. 

A  record  of  all  of  the  interruptions  to  service  is  kept 
at  both  of  the  stations  together  with  the  cause  of  the  delay, 
its  duration,  and  other  information.     It  is  interesting  to 


Vacuum    type    employed    in    radio    transmission,    especially    for 
the   sending:   end  of  the  radio  linli. 


316  RADIO  FOR  EVERYBODY 

note  that  althouo^h  the  circuit  was  open  to  commercial 
service  during  the  worst  of  the  static  season,  subscribers 
had  but  Httle  or  no  difficulty  in  using  the  circuit.  Trans- 
mitting frequencies!  of  400  and  470  meters  were  chosen  for 
the  stations  after  an  extensive  survey  of  the  ether,  so  that 
the  telephone  would  cause  the  least  interfernce  to  and  be 
interfered  w^th  the  least  by  radio  stations  in  the  vicinity. 
Some  trouble  was  experienced  from  the  Avalon  spark 
station  located  about  one  mile  from  the  receiving  station. 
Avalon  transmits  on  300  meters,  while  the  Pebbly  Beach 
station  had  its  receiving  apparatus  tuned  to  470  meters. 
Upon  investigation  it  proved  that  the  wave  emitted  by  the 
spark  transmitter  was  a  broad  one,  and  that  when  the 
wave  is  kept  sharp  and  within  certain  definite  limits  of 
purity,  so  to  speak,  little  or  no  trouble  is  experienced  from 
this  station. 

The  circuit,  due  to  the  choice  of  sites,  directional  char- 
acteristics of  the  loop  antennas,  and  selectivity  of  the 
radio  receivers,  is  quite  free  from  interference  and  it  is 
only  occasionally  that  an  interfering  spark  signal  is  heard. 
The  harmonics  from  the  Poulsen  arcs  installed  at  the 
Naval  Radio  Stations  at  San  Diego  and  Englewood,  Cali- 
fornia, have  given  rise  to  some  trouble.  If  the  arc  har- 
monic beats  with  the  radio  carrier  and  side  frequencies  of 
the  radio  telephone  station  at  either  an  audible  or  nearly 
audible  rate,  the  quality  of  the  speech  over  the  circuit 
may  be  affected  materially.  This  is  in  effect  the  same 
result  which  obtains  when  speech  signals  are  received  on 
an  ordinary  heterodyne  receiver  when  the  local  oscillator 
is  not  adjusted  to  the  same  frequency  as  that  of  the  trans- 
mitter. Although  this  trouble  can  be  eliminated  as  soon 
as  it  is  discovered  by  shifting  the  carrier  frequency  of  the 
radio  telephone  transmitter  a  few  thousand  cycles,  it  is 
obvious  that  in  the  future,  when  many  stations  may  be 
expected  to  be  operating,  this  difficulty  must  be  eliminated 
in  a  more  elaborate  manner. 

The  radio  link  also  provides  for  a  full  duplex  radio  tele- 
graph circuit,  capable  of  sending  and  receiving  messages 
in  two  directions  at  the  same  time.     Ordinary  telegraph 


Special  form  of  switchboard   and  radio  controls  for  connecting 
the    radio    link   with    the    regular    telephone    system. 


318  RADIO  FOR  EVERYBODY 

instruments  are  used  at  the  terminals  and  ordinary  tele- 
graph lines  lead  to  the  radio  installation.  This  duplex 
telegraph  service  operates  simultaneously  with  the  radio 
telephone  with  no  interference  whatsoever. 

The  Radio  Links  at  Sea 

The  day  is  not  far  distant  when  every  passenger 
steamer  at  sea  will  be  just  as  much  within  reach  of  the 
regular  telephone  system  and  just  as  much  an  integral 
part  of  that  system  as  the  modern  city  apartment.  There 
is  nothing  new  in  this  prophecy :  it  has  been  talked  about 
and  virtually  promised  ever  since  radio  telephony  came 
into  existence  a  decade  and  a  half  ago.  But  today  we 
are  making  very  substantial  progress  toward  the  early 
realization  of  telephony  from  ship  to  shore,  along  with 
all  the  other  things  promised  for  radio  telephony. 

Already  we  are  telephoning  to  sea  over  the  regular  tele- 
phone lines.  Experiments  are  being  carried  on,  and  while 
much  remains  to  be  done  in  the  wa,y  of  perfecting  and 
refining  the  various  details  of  this  combined  telephone  and 
radio  telephone  system,  the  results  indicate  that  the  idea 
is  feasible  and  most  likely  practical.  A  person  talks  over 
the  regular  telephone  line  and  listens  in  the  same  manner 
as  usual.  The  other  person  on  board  ship  also  speaks  in 
the  usual  manner.  Aside  from  occasional  interference 
from  other  radio  transmitters,  especially  radio  telegraph, 
there  is  nothing  to  indicate  that  the  conversation  is  other 
than  an  ordinary  telephone  conversation. 

Recently  an  official  of  the  Bell  System  was  called  to  the 
telephone  at  his  residence  in  New  Canaan,  Conn,,  to 
answer  a  call  from  Captain  Rind,  who  was  on  his  ship 
the  "America"  of  the  United  States  Line  as  it  approached 
New  York.  At  the  time,  the  "America"  was  still  24  hours 
from  port,  or  about  370  miles  distant. 

"Hello,   this  is  Captain  Rind." 

"Captain,  this  is  Mr.  Thayer  of  the  telephone  company. 
I'm  up  in  New  Canaan.  I  understand  you  are  three  or 
four  hundred  miles  at  sea." 


I? 


OS 
o  2. 

^  i 


L  ^       1^^?  '^^^^m^^Kmmm^^mmm 

320  RADIO  FOR  EVERYBODY 

"Yes,  we  were  370  miles  from  Ambrose  light  at  7  :30. 
We  expect  to  dock  tomorrow  evening  at  7  or  8/' 

"What  kind  of  a  trip  are  you  having?" 

"W^e're  having  a  good  trip  for  this  time  of  the  year." 

''Well,  I'm  glad  to  have  had  the  pleasure  of  speaking 
to  you.  I  think  It  is  fine  that  we  can  meet  and  talk  this 
way." 

That  was  how  the  conversation  ran.  Over  100,000  per- 
sons heard  the  conversation ;  for  the  radio  link,  connecting 
the  wire  telephone  system  with  the  ship  radio  set,  makes 
use  of  radio  waves  that  may  be  intercepted  and  heard 
with  the  usual  radio  receiving  set.  It  may  be  that  at  some 
future  date  some  combination  of  wave  lengths  will  be  em- 
ployed to  make  the  radio  telephone  link  more  or  less  pri- 
vate; but  for  the  time  being  the  conversations  are  more 
or  less  public  because  of  the  large  number  of  amateur 
receiving  sets  within  range. 

Preliminary  to  her  last  voyage  to  Europe,  the  steam- 
ship "America"  had  been  equipped  with  a  radio  tele- 
phone set.  Throughout  the  eastward  trip  tests  were  car- 
ried out  between  the  ship  and  the  radio  telephone  station 
of  the  Bell  System  located  at  Deal  Beach,  N.  J.,  some  33 
miles  south  of  New  York  in  an  air  line.  These  tests  were 
overheard  night  after  night  by  numerous  radio  amateurs 
along  the  North  Atlantic  coast,  and  led  to  many  questions 
concerning  their  purpose.  Similar  inquiries  were  antici- 
pated upon  the  return  of  the  ship  and  it  was  thought  de- 
sirable by  the  telephone  officials  to  advise  the  public  by 
means  of  a  demonstration  before  representatives  of  the 
press. 

The  evening  of  March  5th  was  selected  as  the  time  for 
this  demonstration,  since  the  ship  was  scheduled  to  be  then 
between  350  and  400  miles  from  port,  a  distance  consid- 
ered to  be  the  fair  working  range,  under  normal  atmos- 
pheric conditions,  for  the  radio  transmitters  both  on  board 
ship  and  at  Deal  Beach.  The  success  of  the  demonstration 
proved  that  the  time  had  been  well  chosen ;  for,  with  the 
exception  of  10  or  15  minutes  during  which  the  wireless 
waves  were  subject  to  "fading,"  as  the  radio  engineers  say. 


RADIO  FOR  EVERYBODY  321 

telephoning  between  the  ship  and  shore  proceeded  without 
the  shghtest  difficulty. 

Tying  Ships  and  Shore  by  Telephone 

The  schematic  drawing  on  pages  322  and  323  gives  a 
general  idea  of  how  these  experiments  in  ship-to-shore 
telephony  have  been  carried  on.  The  reader  will  note  that 
two  separate  stations  are  being  used  on  the  Jersey  coast. 
Deal  Beach  being  the  transmitting  station  and  Elberon  the 
receiving  station.  For  those  who  are  more  technically  in- 
clined, it  might  be  pointed  out  that  the  wire  circuit  was 
operated  on  the  four-wire  principle  between  Walker  Street 
and  the  radio  stations,  and  on  the  ordinary  two-wire  prin- 
ciple from  Walker  Street  to  New  Canaan.  A  hybrid  coil 
and  balancing  network,  such  as  forms  an  essential  part 
of  all  telephone  repeaters,  established  the  union  between 
the  two-  and  four-wire  circuits. 

The  steamship  ''America,"  belonging  to  the  United 
States  Shipping  Board  fleet,  is  a  28,000-ton  vessel  en- 
gaged in  passenger  service  between  New  York,  Cherbourg, 
and  Bremen.  On  the  trip  of  which  we  are  writing  she 
carried  a  large  booking  of  passengers  who,  during  the  pro- 
gress of  the  tests,  not  only  manifested  considerable  inter- 
est in  them  but  also  expressed  in  no  uncertain  terms 
their  willingness  to  talk  with  persons  on  shore  should  they 
be  given  the  opportunity.  These  passengers,  in  turn,  had 
many  friends  in  this  country  who  were  equally  anxious  to 
communicate  with  them;  indeed,  the  engineers  in  charge 
of  the  Deal  Beach  station  reported  an  avalanche  of  more 
telephonic  calls  than  they  took  time  to  count  from  parties 
who  wanted  permission  to  talk  with  friends  on  board. 
One  of  these  requests  actually  came  by  telephone  from  as 
far  west  as  Chicago. 

The  demonstration  not  only  brought  out  the  possibilities 
of  ship-to-shore  communication,  but  also  illustrated  its 
shortcomings — shortcomings  which  are,  in  large  measure, 
characteristic  of  radio  in  all  its  forms.  At  regular  inter- 
vals throughout  the  test,  which  lasted  for  over  an  hour, 
intelligible  communication  with  the  ship  was  prevented  by 


General  scheme  ox  the  radio  link  as  employed 
to  couple  up  a  ship  with  the  wire  telephone 
system.  This  particular  diagram  applies  to 
the  experiments  conducted  by  the  American 
Telephone  &  Telegraph  Company  between  the 
steamer  "America"  and  the  Deal  Beach  sta- 
tion. The  arrangement  in  the  large  circle 
represents  the  coupling  system  at  the  test 
room  in  the  Xew  York  headquarters  of  the 
telephone  conxpany.  Two-way  communication 
is  maintained  with  the  radio  link,  by  using 
a  transmitting  and  a  receiving  station  at  the 
land  end,  as  depicted. 


324  RADIO  FOR  EVERYBODY 

interference  from  spark  stations,  most  of  which  were  on 
vessels  at  sea,  the  spark  stations  near  New  York  very 
generously  having  stopped  their  sending  during  the  period 
of  demonstration.  The  elimination  of  interference  be- 
tween stations,  all  engaged  in  carrying  commercial  busi- 
ness, is  one  of  the  important  technical  problems  of  radio 
still  waiting  solution. 

Another  limitation  of  the  radio  telephone  was  forcibly 
brought  out  by  the  number  of  telephone  calls  which  came 
in  from  persons  who  said  they  had  simple  radio  sets  in 
their  homes  and  were  listening  in  on  the  whole  conversa- 
tion between  the  speakers  on  shore  and  on  the  ship.  A 
telephone  message,  once  it  has  been  given  to  the  radio 
transmitter  for  propagation  through  the  air,  is  virtually 
public  property,  and  as  upwards  of  one-half  million  radio 
amateurs  throughout  the  country  know,  it  is  the  simplest 
matter  in  the  world  to  listen  in  on  such  a  message.  How- 
ever, there  are  ways  in  which  secrecy  may  ultimately  be 
obtained  for  the  radio  link  of  a  telephone  system. 

Moreover,  atmospheric  conditions  exert  a  marked  in- 
fluence upon  the  ease  with  which  a  radio  message  travels 
through  space.  These  conditions  vary  greatly  from  day  to 
day  and  from  hour  to  hour.  This  can  well  be  illustrated 
by  the  observations  which  have  been  made  in  connection 
with  the  radio  link  of  the  telephone  system  operating  be- 
tween Long  Beach,  California,  and  Catalina  Island.  The 
distance  between  the  mainland  and  the  island  is  30  miles, 
and  the  sets  have  been  made  sufficiently  powerful  to  trans- 
mit speech  across  this  distance  under  the  most  unfavorable 
conditions.  On  the  other  hand,  it  has  been  found  that 
this  amount  of  power  is  sufficient  under  exceptionally 
favorable  conditions  to  make  these  messages  readily  audi- 
ble in  New  Zealand,  5,000  miles  away.  One  of  the  most 
difficult  radio  problems  the  telephone  engineers  have  en- 
countered is  the  transmission  of  a  fixed  quantity  of  cur- 
rent over  the  telephone  lines  in  spite  of  the  extremely 
variable  intensity  of  the  radio  signals  which  are  to  be 
relayed  over  these  lines. 

Another  atmospheric  phenomenon  which  is  a  source  of 


no 

PS. 
If 

^^ 

9 


So 


—  3  3* 
I  =  * 


id 

•    «  3 


.3 


S5 


so 


•5^ 


Bsp 


326  RADIO  FOR  EVERYBODY 

most  serious  disturbance  to  radio  transmission  and  which 
thus  far  has  baffled  all  attempts  to  eliminate  it,  is  the  so- 
called  "static."  Fortunately,  for  the  demonstration  we 
have  just  described,  there  was  very  little  static  present. 
Its  occurrence  varies  greatly  with  the  season  of  the  year, 
imd  in  the  northern  hemisphere  is  particularly  trouble- 
some during  summer.  Indeed,  there  are  hours  and  even 
days  together  when  all  but  the  strongest  radio  signals  are 
obliterated. 

The  radio  link — the  spanning  of  space  between  bits  of 
regular  telephone  system — must  come.  The  difficulties  in 
the  way  of  everyday,  practical  ship-to-shore  communication 
are  numerous  and  formidable,  but  they  are  certain  to  be 
brushed  aside  just  as  so  many  other  obstacles  in  radio 
have  been  overcome. 

And  What  of  the  Future? 

To  say  that  the  radio  link  between  land  units  and  be- 
tween land  units  and  ships  at  sea,  is  here  in  a  practical 
and  workaday  way  would  be  to  exaggerate  the  facts  in 
the  case.  Much  remains  to  be  done,  as  any  one  who  has 
listened  in  to  the  experiments  must  realize.  The  inter- 
ference from  other  radio  stations,  the  static,  the  fading 
away  of  a  transmitter — all  these  features  hamper  radio 
telephony  to  a  marked  degree  and  must  be  very  much 
ameliorated  before  we  can  hope  for  a  system  that  will  be  as 
positive  and  reliable  as  our  present  wire  telephones.  Of 
course,  for  short  spans,  like  the  Long  Beach-Avalon  radio 
link,  for  which  a  good  deal  of  power  is  employed  in  view 
of  the  short  distance,  the  results  are  really  reliable;  but 
then  the  radio  link  must  be  capable  of  spanning  many 
hundred  miles,  especially  in  telephoning  to  sea,  if  it  is  to 
be  made  of  some  commercial  value. 

The  question  of  secrecy  is  an  important  one,  for  nobody 
cares  to  be  talking  to  a  relative  or  friend  while  one  hun- 
dred thousand  other  persons  are  listening  in.  Just  so 
long  as  the  messages  stay  on  the  wires,  they  are  private, 
but  at  the  present  stage  of  radio  telephony  the  moment 
these  same  messages  are  passed  through  the  radio  trans- 


328  RADIO  FOR  EVERYBODY 

mitter  they  become  public  property.  However,  this  ques- 
tion of  secrecy  can  be  solved — and  it  will  be  solved,  in 
the  very  near  future.  There  are  several  ways  in  which 
this  end  -can  be  attained.  Perhaps  the  ultimate  solution 
will  be  obtained  by  a  system  of  double  or  triple  waves 
employed  simultaneously  for  the  transmission  of  speech 
so  that  unless  a  person  has  a  receiving  set  which  intercepts 
a  certain  combination  of  waves,  only  a  small  and  almost 
unintelligble  part  of  the  conversation  will  be  detected.  It 
is  also  quite  possible  to  use  a  device  at  the  transmitting 
end  which  continually  alters  the  wave  length  of  the  trans- 
mitted radiophone  waves,  while  the  receiving  set  is  also 
provided  with  a  means  of  altering  its  wave  length  in  step 
with  the  transmitter. 

As  for  static,  it  will  be  with  us  for  many  years  to  come. 
There  have  been  many  so-called  static  eliminators  intro- 
duced from  time  to  time,  and  we  are  assured  over  and 
over  again  that  this  arch  enemy  of  radio  has  been  banished 
for  all  time.  But  the  fact  remains  that  despite  all  kinds 
of  static  eliminators  said  to  be  practical  and  available, 
we  continue  to  be  troubled  by  static  in  our  commercial 
and  amateur  work  alike. 

The  wire  telephone  was  not  perfected  over  night,  and 
we  cannot  expect  the  radio  telephone,  which  dates  back  to 
but  a  fev/  years  in  point  of  real,  practical  development, 
to  evolve  into  perfected  communication  overnight.  Then 
the  problems  of  transmitting  through  space  are  consider- 
ably more  numerous  and  involved  than  those  of  the  wire 
telephone.  It  is  going  to  take  time,  but  the  day  must 
come  when  the  radio  telephone  will  be  an  everyday  con- 
venience. 


INDEX 


"A"  Battery  121 

Abbreviations,    Radio    171 

Aerial    13,  24 

Aerial  and  Antenna,  Separate 215 

Aerial  and  Ground 14.  95 

Aerials,   Types  of 212-215 

Air-Mail   Radio   Service 77 

Amateur    Stations    172 

Alternating    Current    24 

Ammeter   24 

Ampere 26 

Amplifier     26.  195 

Amplifying    Tubes     127,  193 

Amplifier,  Two-Stage 182 

Amplifier    Units    191 

Amplifiers,  When  and  Where  to  Use 189 

AmpHtude    26 

Announcer,  The    51 

Antenna 13,  280 

Antenna  in  City 99 

Antenna,  Various   Types 101,  102 

Antenna,    Erecting    95,  147 

Antenna  Materials   96 

Arlington,  Va.,  to  Paris,  Experiments 50 

Atmospherics     26 

Audio  Frequencies    26 

Audio   or   Radio   Frequency — Which? 182 

Audio   Frequency  Amplifier 184 

Avalon-Los  Angeles   Link    272,  311 

Battery  A   121 

Battery  B 26,  121 

Battery,  Storage  122,  124 

Beats    140 

Bed  Springs,  Use  of 150 

Boat,    Radio-Controlled    250 


330  INDEX 

Boxing  Contest,  Transmission  of 71 

Broadcasting    1,  26,  59,  61 

Broadcasting  Schedule    82 

Broadcasting    Station     55, 68 

Bureau  of  Markets  and  Crop  Estimates 85 

Business,  Radio  in • 259 

Buzzer    Practice    Set 167,  190 

Buzzer  Test   -. 146 

Cage,  Aerial   241 

Call  Letters    176 

Capacity    (Abbreviated    C) . 12,  26,  27 

Cascade   Amplification    27 

Choke  Coil 27 

Chopper    241 

Circuit    28,  129 

Close   Coupling   ". 28 

Code,   International    165 

Code,  Learning 166,  168 

Coil,    Loading 113,  116 

Combination   Set    145 

Communication,  Telephonic   54 

Compact   Inductance    130,  132,  134 

Compass,    Radio    252 

Concentrated  Inductance    • 132 

Concert,    Radio-Phone    70 

Condensers     12,  28,  220,  222 

Condensers  Transmitting    220 

Condenser,  Variable 116 

Congress  and   Radio 92 

Connections,   Simple    28,  112,  113 

Continuous  Wave    (Abbreviated    C.  W.) 28 

Counterpoise     28,  104 

Cost  of   Sets  and   Parts 21,  291 

Coupler    29 

Crops  and  Market  Reports 75,  79 

Crystal  Detector    29,  110,144,  285 

C  W  and  C  W  Signals '.  140,  162 

C  W  Waves,  Buzzer  Modulated 240 

C  W,  Popularity  of 233 

C  W   Transmitters - 235,  238 

Damped  and  Undamped  Waves    • 9,  207 

Department    Stores   and   Radio 67 

Detector     30 

Detector,    Crystal    110 

Detector    Tube    128 

Dielectrics    220 

Direct  Current  (Abbreviated  D.C.) 30 


INDEX  331 

Distance  in   Radio   Communication 6 

Dry   Batteries    123,  297 

Electrical    Symbol    25 

Electrodjaiamic  Receiver   194,  200 

Electron    30 

E.  M.  F 30 

Ether   • 30 

Experimental    Stations    50,  172 

Filament  Battery 121,  154 

Flat-Top    Aerial    30 

Frequency    30 

Future   of  Wireless 65 

Government  Use  of  Radio 91 

Grid,  Employment  of 181 

Grid    Leak    32,  30Q 

Ground 32,  95,  102,  151 

Ground  for   Transmitting    215 

Guided  Wave  Transmission    256 

Harmonics .  .  .  • 32' 

Head  Sets    135 

Henry    32 

Hertzian  Waves   32 

Hook-Ups 32,  152 

Horn,    Metal    193 

Hot   Wire  Ammeter 33 

Hydrometer,  Use  of 154,  156 

Impedance     33. 

Inductance    (Abbreviated   L) 33 

Inductance    Coils    135 

Installing  the   Receiving  Set , 149 

Instruments,    Cost    of 23 

Instruments,    Range    of 23 

Insulator    33,  98,  214 

Insulator,  Lead-in    103 

Jamming   Signals 211 

Kilowatt  (Abbreviated  K.W.) 33- 

Lead-in    Insulator    103. 

Lightning 105 

Lightning    Switch    105,  282 

Long  Island  Radio   Central 265 

Loop    Antenna    ■ 33,  106,  107,  155 

Loose-Coupler    130,  131,  292- 

Loud-speaker    33,  192,  194,  197,  198,  199 

L-Type   Antenna    101 

Magnavox    204 

Map  of  Radio  Inspection  Districts 175 

Marine  Type  of  Transmitter 225 


532  INDEX 

Market  News  Service  75,  76 

Megohm 33 

Mica  Condenser    223 

Microfarad    (abbreviated   mfd.) 33 

Microphone     33 

Milliampere   (abbreviated  M.A.) 34 

Modulator  Tubes    246 

Music,  Transmission   of 61 

Natural    Frequency 34 

News,    Distributing   the 74 

Night-Letters     266 

Ohm   34 

One  Step  Radio  Frequency  Amplifier 187,  188 

Operating  the  Radio  Receiving  Set 143 

Operation,    Pointers    on 159,  160,  161 

Oscillating   or    Vibrating    Currents 11,  34 

Plate  Battery 121 

Phonograph  Attachment    192,  202 

Post   Office  Department  and  Radio  Service 77,82 

Potential   (See   EMF  and  Volt) 34 

Primary  and    Secondary   Circuits 129 

Programs,    Wireless    52,  53 

Radiation    34 

Radio  Apparatus,   Fitting 19 

Radio   Communication,   Elements   of 14 

Radio    Communication    Laws 174 

Radio  Compass 252 

Radio   Control 248 

Radio   for    Farmers 49 

Radio  Frequencies    34 

Radio  Frequency   Amplifier    183,  184,  186,  190 

Radio  in  the  Home 41 

Radio  Inspection   Districts    174,  175 

Radio  License    170, 172 

Radio  Link     50.  56,  307,  311,  318 

Radio-Phone 1,  40 

Hadio-Phone,  Broadcasting   39,  58 

Radio-Phone  to  Dots  and  Dashes 164 

Radio  Reception    93 

Radio  School    170 

Radio  Signals    16,  18 

Radio  Telegraphy,  Use  of 84 

Radio  Telephony  in  Simple  Form 243 

Radio  Transmitter,  What  it  Does 206 

Radio  Waves 15 

Range   of   Instruments 23 

Reactance    (See    Impedance) 34 


INDEX  :m 

Receiving  Equipment    20,  93,  109,  12a 

Receiving  Set,    Simple ill 

Receiving  Station    57 

Reception,   Radio 93 

Rectifier    34 

Rectifier  and  Stepdown  Transformer 158 

Regenerative   Circuit    35 

Regenerative   Reception    138, 142" 

Regenerative  Set    138 

Remote   Control    248 

Resistance    35 

Resonance    35 

Rheostat 35 

Rockv  Point  Station 266 

Rotary    Gap 227 

Secondarv  and  Primary  Circuits 129 

Selectivity    35 

Self   Amplification    138 

Sets.   Receiving   Ill 

Sharp  Tuning 36 

Sharp  Waves 216 

Signals.   Radio    16 

Sliders     113 

Solenoidal   Loop 107 

Spark   Gaps    224,  227 

Spark  Interference    163 

Spark  Signals   and   C  W   Signals 162' 

Spiral    Loop 107 

Standard  Symbols    2.5 

Static   (See"  Atmospherics)    .26,  36. 

Stepdown    Transformer    158 

Storage  Battery    36,  122 

Storage  Batteries,  Rating  of    156 

Storage  Batteries,  Recharging 156' 

Storms     105 

Studio,    Broadcasting    68 

Symbols,    Standard    25^ 

Telephone  Receivers    ' 133 

Telephone  Receivers,    Limitations    of 201 

Telephone  System  and  Radio  Link 50 

Tickler  Coil   138,  140- 

Tikker    , 140 

Time   Signals 86,  89 

Traffic.    Long    Distance 274 

Transatlantic  Radio  to  Transcontinental  Telephone 78 

Trans-Atlantic  Station,   Operating 268 

Trans-Continental  Telephone    66. 


334  INDEX 

Transformer    36,  186 

Transmission,  Code    .  , : .  .  .        80 

Transmitter 17 

Transmitter   Layout    230 

Transmitters   Sharply   Tuned 216 

Transmitting  Condensers    220 

Transmitting  Tubes    243,  245 

T-Type  Antenna .      102 

Tuner     136,  284 

Tuning    8,  36 

Tuning  Coil    117 

Tuning   Inductance    211 

Tuning,   Simple  Sets    • 146 

Tuning  Transmitters    42,  219 

Umbrella  Type  Antenna 101,  102 

Undamped  Transmitter    10 

Undamped  Waves    9,  36 

Undamped  Wave  Transmitter 10 

Vacuum-gap,  Lightning  Protector 106 

Vacuum    Tube     36,  37,  118,  121,  125,  154,  292,  299,  313,  315 

Vacuum  Tube,  Amplifier   127 

Vacuum  Tube  as  Transmitter 229 

Vacuum  Tube  Oscillator  Method 236 

Variable  Condenser   116,  295 

Vario-Coupler    130 

Variometer 37,113,  114,  301 

Velocity   of   Waves 37 

Vibrating  or   Oscillating  Currents 11 

Voice  Carrying 203 

Voice,  Radio    39 

Voice,  Transmission   of    60 

Voltmeter    37 

Voltmeter,   Use   of 156 

V-Type   Antenna    101 

Watt    (abbreviated  W) 37 

Wave  Length    7,  37 

Wave  Lengths,  Questionnaire  on 81 

Wave  Aleters    219 

Wave  Transmitter  Damped    221 

Waves,  Damped  and  Undamped 9 

Waves,  Transmitting 17 

Weather  Reports    88 

Wire  and  Wireless  Work  Together 272 

Wired  Wireless    254 

Wireless  Telephon}^   Early 44 

Wiring 115,  288 

World  Communication    278 


pBjj^        Date  Due 

M  1  0   ,Qq| 

s 
^ 

f) 

1 


BOSTON  COLLEGE 


3  9031   01460937  4 


TK6550 


dup. 
7/27/82 


T escarbcura,  Austin  C 
Radio  for  ever^ody 


L.  v.. 


BOST    ^  COLLEGE  LIBRARY 

^SITY  HEIGHTS 
'^ILL,  MASS. 


*-'  .  two  weeks  and  may  be 

lenewe*.  period,  unless  reserved. 

Two  cents  u         iS  charged  for  each  book  kept 
overtime. 

If    you    cannot   find  what    you    want,   ask  the 
Librarian  who  will  be  glad  to  help  you. 

The  borrower  is  responsible  for  books   drawn 
on  his  card  and  for  all  fines  accruing  on  the  same. 


f> 


